TALES OF
METAL
RESILIENCE
ROBERT A.
FRANCIS
Resilience is a popular buzzword today, used in fields as diverse as politics, psychology and
ecology to describe the ability to resist adversity. But its original use was in engineering to
describe resistance of a material to deformation from applied stress. So, its use to describe
resistance to corrosion is not a big reach. Those of us in the corrosion industry are aware of
the damage caused by corrosion. But we also know it is possible to mitigate. This series of
short items attempts to paint a positive and optimistic picture by reviewing some
interesting and historic examples of how corrosion can and has been defeated.
Chapter
1
2
3
4
5
6
7
8
9
10
11
12
Title
Element 77 - Complete Corrosion Resistance?
Space - Free from Rust?
Tutankhamun’s Iron Treasure
Roman Nails Resist Rust
Aircraft Preservation in the Arizona Desert
Delhi’s Rust-free Iron Pillar
A Stainless Steel Architectural Marvel
The Unsung Building Material
Zinc Silicate: Liquid Rock for Years of Protection
Ever-present Epoxy Coatings
Boilers, Steam and Water Treatment
The Birth of Corrosion Science
Page
1
3
5
7
9
11
13
15
18
20
22
25
Copyright © 2024
Early versions of these articles first appeared in Materials Performance, March 2018 to April 2019. Product
names mentioned in this document may be trademarks or registered trademarks of their respective companies
and are hereby acknowledged. No copyright infringement is intended.
Chapter 1
Element 77 - Complete Corrosion Resistance?
Let’s start at the beginning. We
know that corrosion is a reaction
between a material and its
environment, so why not have a
look at the most corrosion
resistant metal in the periodic
table. According to the ASM Metals Handbook, and numerous other sources, that
superlative honour goes to one of the rarest elements, Iridium. It is resistant to alkalis as
well as highly aggressive acids as shown in the table. The only substances which will dissolve
the metal are molten sodium cyanide and potassium cyanide.
Corrosive
Gold
Platinum
Concentrated Hydrochloric Acid at 100°C
o
✓
Concentrated Nitric Acid at 100°C
x
✓
Aqua Regia* at 100°C
x
x
Moist chlorine gas at Room Temperature
x
o
✓: Resistant
o: Some attack x: Severe attack
* a mixture of concentrated nitric and hydrochloric acids
Iridium
✓
✓
✓
✓
Iridium is a hard, brittle member of the so-called platinum group of
metals in the periodic table. It is only a fraction less dense than the
densest element, its neighbour osmium in the periodic table and
approximately double that of lead. It was discovered by Yorkshire
chemist, Smithson Tennant (1761-1813) in 1803, by separating and
analysing the residue left after dissolving impure platinum in aqua
regia. It was named after Iris, the goddess of the rainbow, because its
salts were so colourful.
Smithson Tennant
World production of iridium is small, only a few tonnes a year, and it is
one of the least abundant and most expensive metals. It is produced as a
by-product of nickel smelting and has few applications as a pure metal. In
such a form, it is used for electrodes in high performance spark plugs and
crucibles for the preparation of single crystals of certain electronic and
optical glasses. As an alloying element, it increases the corrosion
resistance of titanium and palladium and the strength, hardness and
corrosion resistance of platinum. Despite its corrosion resistance, you are
most likely to come across iridium indirectly. It is one of the mixed metals
in Mixed Metal Oxide (MMO) coated titanium impressed current anodes.
1
Those involved in non-destructive testing may come across iridium-192 as an isotope in
radiography.
There are two interesting facts regarding iridium not related to corrosion properties:
• Until recently, the only remaining base unit still defined by an artefact rather than by
a fundamental constant of nature was the kilogram, which was defined as the mass
of a cylinder of platinum with 10 per cent iridium kept under nested bell jars at the
International Bureau of Weights and Measures near Paris. In this case, the iridium is
added to increase the hardness to resist wear during cleaning. A new definition of
the kilogram based on fundamental physical constants was adopted in 2018.
•
Iridium is probably best known because of its association with the likely cause of
extinction of the dinosaurs. The rocks in the boundary layer between the Cretaceous
and Tertiary geological periods, laid down about 65 million years ago, contain a
higher proportion of this element than other rocks. An iridium-enriched meteor is
believed to have hit the Yucatan peninsula off Mexico, and dust from the impact
caused darkening of the skies which wiped out most large animals.
Why metals corrode (and some don’t)
When a metal corrodes, its atoms lose electrons and the chemical nature completely changes from a
solid, shiny substance to charged ions which dissolve in a solution. These ions often react with other
compounds to form rust or other corrosion products, but it is this first stage that is critical. Different
metals have different tendencies to lose these electrons. The dozens of different metallic elements can
be placed in a list which shows their relative ability to lose electrons. A simplified list with some
common metals, known as a reactivity or electrochemical series, is shown below. It is very difficult to
remove electrons from those at the top, such as gold and platinum. But those at the bottom, such as
calcium and sodium are very reactive and rarely found in
their native form. In between, metals show an increasing
degree of reactivity moving down the list.
Chemists call the reaction which removes electrons
oxidation. A chemical or chemicals have to react with the
metal to take up electrons from the oxidation reaction. As
the name suggests, oxygen can take up the electrons and
form a metal oxide. There are many other compounds of
varying ability that can oxidise metals. These are shown in
the right-hand column. Water will oxidise metals at the
bottom of the reactivity series, while acids are necessary
to corrode those in the middle. Very strong oxidisers are required to attack the stable metals at the top.
The series can explain the relative resilience of many of the metals, but there are some anomalies.
Aluminium, chromium (which gives stainless steel its resistance) and, especially, titanium are known to
be much more resistant than their position in the series would suggest. These metals form a protective
oxide film in many environments so can resist many oxidisers. But this oxide film, known as passive
protection, can break down under certain conditions, such as a high concentration of chloride ions.
Metals arriving from outer space bring us to our next tale in success in resisting corrosion.
2
Chapter 2
Space - Free from Rust?
Corrosion, being a reaction between a material and its environment, can be minimised by
creating a benign environment, rather than looking at expensive materials such as iridium.
And, in theory, it is not hard to find a very benign environment – simply head upwards for
one hundred kilometres or so into space. No water, no oxygen and no chemicals to cause
corrosion. Of course, there will be all sorts of other trepidations such as temperature and
pressure extremes, fast moving space dust and rocks, high UV and radiation exposure, any
of which may destroy many materials. But true chemical corrosion is unlikely to be a
concern.
If, or when, a base is set up on
the moon, inhabitants will
need to protect their
materials from the natural
environment. The high UV
radiation will damage many
organic materials such as
paints and plastics. The sharp
moon dust, which is not
subject to wear and rounding
from weathering we see on
earth, will destroy exposed
bearings and any other
contacting surfaces. The
Moon exploration as imagined in an early 1960s children’s book.
extremes of temperature will
cause thermal fatigue of metallic and non-metallic materials. The absence of corrosion from
rain, oxygen and marine salt is unlikely to be much comfort to engineers designing human
habitation and facilities on the moon.
The spacesuit worn by Neil Armstrong on the moon has been found to be degrading and
currently undergoing restoration. But it is neither the space nor the moon environment that
is the culprit. Plasticisers have from leached from the PVC, rubber has broken down and
degraded, physical damage has arisen due to poor handling and storage and sweat from the
astronaut activity have all combined to destroy plastic and metal components. It is hoped
that conservation efforts will significantly slow such damage, but it does seem a shame that
one of the most important symbols of our age may not be seen by our descendants.
Our sister planet Venus may also seem to be a corrosion nightmare. A number of Russian
Venera probes landed on the surface in the 1970s and 1980s, but only sent back data for an
hour or so. Venus does have corrosive sulfuric acid in its upper atmosphere, but at the
3
surface it is the high temperature (about
450°C) and high pressure (about 90 times
that on earth) that would have destroyed
these landers. The titanium spacecraft would
probably now be twisted bits of metal on the
surface, but corrosive metal loss would
probably be minor.
Away from physical problems of heat and
pressure, space is remarkably benign. The
building blocks of our solar system are rocky
and metallic asteroids which have been circling the sun for billions of years. Metallic
asteroids are largely made of iron, with about 10 per cent nickel and traces of other
elements (such as iridium in the meteor that caused destruction of the dinosaurs) and only
have a surface tarnish from the solar wind after all those years. The picture shows a slice of
the Muonionalusta meteorite found in
Sweden in 1906. (The etch, known as a
Widmanstädten pattern, arises from the very
slow cooling of the metal during its
formation). Very little surface oxidation has
taken place as it was buried deep after it fell
to earth about a million years ago. Such an
alloy would readily corrode on earth and
meteorites found on the surface oxidise
when exposed to water and oxygen. But in
space they remain largely in the state they
were when they formed at the birth of the
solar system.
We return to earth but stay with meteoric iron for our next corrosion-free artefact and see
an example of how iron can remain rust-free for thousands of years.
4
Chapter 3
Tutankhamun’s Iron Treasure
When he discovered the tomb of Tutankhamun in 1922, Howard Carter was asked what he
could see. “Wonderful things!” he replied as he peered into the treasure-filled tomb. Of the
many “wonderful things” Howard Carter found, a small iron dagger may seem insignificant
compared to the numerous gold, silver and beautifully-coloured objects that the boy king is
famous for. But to the corrosionist, this item is remarkable because it just may be the oldest
intact iron artefact known.
The iron dagger, about 34 centimetres long with a gold handle, was found in the
sarcophagus of the ancient Egyptian king, who was buried in 1320 BC. Researchers from the
University of Pisa and other establishments in Italy and the Egyptian Museum recently
analysed the blade using non-destructive x-ray fluorescence and found that the composition
was of meteoritic iron with about 10 per cent nickel and 0.6 per cent cobalt. Ancient
peoples used meteorite iron for various tools, weapons and jewellery, although this dagger
shows a high degree of metalworking skill and is probably the finest example of its type.
Despite being buried for nearly 3,300 years, the blade is in excellent condition, with only
minor evidence of corrosion as shown in the photograph. The inset shows the surface is not
completely smooth or clean, but no analysis of the surface contamination has been
reported. There are a number of possible causes for this surface stain. Iron meteorites are
not completely metallic, and there may have been non-metallic silicate or other inclusions.
The method of iron working is unknown, but heating and forging may have embedded
charcoal or other impurities in the surface. Finally, the dagger was actually in the
sarcophagus next to the mummified body. Mummification involved packing the body with a
rock salt material, natron, to desiccate the body and this corrosive material along with
bodily fluids may have caused some initial corrosion before completely drying took place.
Any or all of these may be the culprit for the surface defects.
While 10 per cent or so of nickel does reduce the corrosion rate of iron somewhat
compared to mild steel, it would still be expected to behave similarly to modern steels. If
exposed to the atmosphere or soil, even in an environment as arid as that in Egypt, it would
Daniela Comelli et al, “The meteoritic origin of Tutankhamun’s iron dagger blade”, Meteoritics & Planetary
Science 51, Nr 7, 1301–1309 (2016)
5
rust and little if any of the original metal would be left. An ancient meteoric iron dagger
found at Alacahöyük in Turkey, admittedly a thousand years older than that found in
Tutankhamun’s tomb, no longer contains any metallic iron. X-ray investigations show this
artefact has completely rusted away, although the gold hilt is still intact. It is not the nickel
in the iron that has allowed Tutankhamun’s dagger to remain intact but rather the very dry
conditions in the tomb.
The Valley of The Kings where pharaohs
were buried is a very dry environment. as
the picture shows. Egyptian tombs were
completely sealed once the complex
embalming and funeral process was
completed. Any moisture would quickly
react with wood or other contents on the
tomb. The air would remain dry while the
tomb remains undisturbed, preventing
not only damage to the iron dagger, but
to wood and other organic items. Sadly,
the humidity from the many tourists that
have passed through the tomb since it opened has caused the remaining items and wall
murals to become damaged.
The Egyptian Museum occasionally sends some of Tutankhamun’s treasures to overseas
museums for special displays, and these treasures include a gold dagger. The iron dagger
stays in Cairo – it is too valuable.
At around the time of King Tutankhamun, ancient Anatolian peoples in what is now eastern
Turkey were making what is one of the most important discoveries in technological history.
The Hittites discovered the difficult process of how to smelt iron from its ore and the Iron
Age was born. Again, most of the iron produced has since rusted away but there are
examples of ancient man-made iron still extant which further show us it is possible to defeat
corrosion. We will look at one of these instances in the next chapter.
6
Chapter 4
Roman Nails Resist Rust
In about 88 A.D., a remote Roman legion based at a fortress at Inchtuthil on the north bank
of the Tay River, not far from what is today Perth in Scotland, was ordered back to the
European mainland. They dismantled or burnt the buildings, smashed the pottery and filled
in drains and sewers to prevent them getting into the hands of the local Caledonian tribes.
Unable or unwilling to transport nearly a million iron nails south with them, they dug a pit
and buried them. Iron could be used for weapons, agriculture and buildings in those days, so
highly prized by the enemy of the Roman legions.
The Romans did a good job of hiding
them, because it was nearly 1900
years before they were found. In
1961, an archaeologist, Professor Sir
Ian Richmond, noticed a region of
different coloured earth at the
Inchtuthil site and, after digging down
some metres, came across a large
corroded mass of iron consisting of
nearly 10 tonnes of nails and other
small iron implements. The picture
shows part of the haul. Further
investigation found that, while the outer items had badly corroded and formed a solid crust
of iron oxide, those on the inside had only a minimal amount of rust on the surface.
The survival of the inner nails was attributed to the protection from corrosive water and
oxygen achieved by barrier created by the outer solid crust. It is not possible to know how
little water or oxygen the inner nails were exposed to over the centuries, but clearly the
amount was very small, or the time it was exposed to these was very short. The
investigation carried out at the site was archaeological, not a corrosion investigation and no
information on water or soil composition or other site chemical factors was obtained.
However, survival of iron on a river flood plain for nearly two millennia gives further
evidence that protecting iron from water or oxygen exposure or both can prevent or at least
minimise corrosion damage.
Many of the nails were sent to museums, corrosion associations and other interested
persons around the world as gifts. Nails of different sizes were mounted in a wooded box
with a clear, plastic lid along with a white plastic label reading “Iron nails from Roman
legionary fortress at Inchtuthil, Perthshire, Scotland AD 83 - 87”. The photograph shows the
box sent to the Australasian Corrosion Association (ACA). This contains five nails of square
shank section with flat, circular heads, of approximate lengths 19.5, 17, 13.5, 9 and 5
centimetres. The nails are now in rather poor condition showing dark flaking rust, especially
7
on the larger nails. Similar boxes appear occasionally on auction and other web sites, and
most of the nails on offer also appear to be severely corroded. Photographs of some nails in
their original condition show far less corrosion. It may be that exposure to humidity over the
past fifty years has caused the small amount of rust that was on them originally to grow.
However, it is more likely that acetic acid fumes from the wooden box has been the main
contributor to the additional corrosion. The fact that corrosion products show black
magnetite, typical of rust formed in severe environments, would support this hypothesis.
Metallurgical investigations of such nails have been carried out since their discovery and
show the microstructure and properties typical of ancient wrought iron objects. Iron could
not be obtained as a liquid from iron ore at temperatures and technology available to the
ancients, but the Hittites who lived in modern day eastern Turkey are believed to have
discovered in about 1300 BC that heating iron ore to around 1200 degrees Celsius in a
charcoal-fuelled furnace reduced the iron oxide to iron metal and hammering enabled the
impurities to be driven out as slag. The result was a
strong and tough metal consisting, as the micrograph
shows, of a mixture of almost pure iron with the
remaining slag forming longitudinal inclusions (known
as stringers) spread throughout the metal. In regions
where the metal contacted the charcoal in the furnace
a higher carbon content was achieved. The technology
spread across the ancient world over subsequent
centuries west to Europe.
As with Tutankhamun’s dagger, the Roman nails show that it is possible to protect a metal
from corrosion by minimising exposure to moisture. For our final lesson in the importance
of keeping metal dry, we return to the present and visit a US Air Force base in the Arizona
desert where the low humidity has enabled the military to minimise corrosion damage to its
old, unwanted and obsolete aircraft.
8
Chapter 5
Aircraft Preservation in the Arizona Desert
The Davis-Monthan Air Force base in Tucson, Arizona, USA, commonly known as ‘The
Boneyard’, is probably the strangest air field in the world. It is the place where the US Air
Force and other federal agencies send their obsolete, unwanted, excess and out-of-service
aircraft, many of which will never fly again. With around 4000 aircraft, it is the largest such
storage and preservation facility in the world, and would be the world’s second largest air
force!
Planes have been stored here since the end of the Second World War. Types range from
F-15 and F-16 fighters, Hercules and Galaxy transports, A-10 attack planes and B-1 nuclear
bombers. The photograph shows C-135 transport aircraft. There are also Harrier jump jets,
experimental aircraft, helicopters and missiles. Not all are intact. Many have been
cannibalised for spare parts, but there are other reasons for destruction. The tails were
sliced off hundreds of B-52s as part of a post-Cold War treaty with Russia to provide proof
they had been scrapped. The parts were scattered on the ground so that Russian satellites
can confirm their destruction.
Although it is commonly perceived as an aircraft
graveyard, a sizable percentage will fly again.
About ten percent are kept in good condition in
case they will need deployment in the future by
the US or its allies. The Australian air force, for
example, sourced a batch of second-hand F-111
bombers, an example shown left, in 1992 in a
bargain-basement deal with the Pentagon.
Some are used as target drones. Many F-4
9
Phantoms, one of the most important aircraft of the post-war period, have ended their lives
in such an ignominious manner. Its chief mission, however, is supplying the air force with
spare parts. Parts from the Boneyard can make the difference between an aircraft being
grounded or operational. Only if it is not required for any reason, and has given all the spare
parts it can, is it scrapped. Many have valuable metals such as gold and platinum.
When an aircraft arrives at the facility, weapons and classified hardware are removed. They
are then thoroughly washed, which is especially important for marine aircraft or those
employed in tropical locations. Fuel is flushed and mechanical parts are protected with a
lightweight oil. Canopies are sealed with a white vinyl latex coating (Spraylat) to protect
cockpit interior from heat and stop the canopies becoming crazed and cracked. Joints are
sealed from dust. Once this is done, the aircraft is towed to its storage area.
The site Tucson provides an ideal site for such a facility. The hard soil is strong enough to
take the weight of a 300 tonne aircraft and makes it easy to move aircraft around without
the need for pavement. However, it is the climate and clean air that minimise degradation
that are most important. It has a very low average humidity of 38%, meaning moisture
contact (time-of-wetness) is minimal. It is hundreds of kilometres from corrosive sea salt,
the hot climate mean de-icing salt is not required to melt snow, and there is no pollution
from heavy industry. As a result, the corrosion rates would be very low. Phoenix AZ, with a
similar environment, has a carbon steel corrosion rate of approximately 5 microns per year,
putting it near the benign end of ISO C2 Low Corrosivity category.
A Note on Humidity and Corrosion
It should be stressed that the low average humidity
figure does not tell the whole story. Like temperature,
relative humidity fluctuates during the day and night
and over the year. The chart shows historical morning
(close to average) and afternoon (close to the
minimum) readings throughout the year (solid lines)
for Tucson, Arizona. However, the maximum humidly
is normally reached at sunrise; well before
meteorologists arrived at work (Historically, such
data were recorded manually before electronic
instruments and data recorders became available).
The maximum humidity can be estimated (dotted
line) as following similar behaviour to average and minimum humidity. This shows that quite high
humidity values can be reached. A still, clear summer night could easily decrease metal
temperatures to well below the dew point, resulting in condensation over the exposed surfaces
leading to corrosion. The low average relative humidity should not be construed as indicating that
corrosive conditions will not arise.
For our next example of resilience of iron against the elements, we will see how ancient
Indian smiths accidently found that impurities in the iron can completely change its
corrosion behaviour and created a famous rust-free icon.
10
Chapter 6
Delhi’s Rust-free Iron Pillar
In the courtyard of a ruined mosque at the Qutub Minar complex not far from Delhi’s
international airport in north India, stands a pillar of iron that has remained rust-free since it
was fabricated in approximately 400 AD. The six tonne pillar was originally forged and
erected in central India during the Gupta period, but moved to its present site about seven
centuries ago. Although the climate in Delhi is not particularly corrosive at about 20 microns
per year for mild steel (ISO category C2), this cannot explain the rust-free condition of the
pillar. As a result of its remarkable state, it has fascinated historians and archaeologists, as
well as those of us with scientific and technical interests, for many years.
The solid iron pillar is about 7 metres high and about 40 centimetres in diameter at the
base. The lower part is rough and pitted where it was once below ground but the rest of the
cylindrical column is smooth and tapers to a decorative bell at the top. An inscription
commemorates the victory of King Chandra over his enemies in the fourth century AD.
There is also damage believe to be from a cannon shot. The massive pillar was not built in
one piece, but rather by hammering together several pieces of hot wrought iron in a process
known as “forge welding”. The composition is not homogeneous, with the carbon content
especially varying widely as with other ancient wrought iron. The average composition is
shown in the table, compared to a typical modern steel of similar carbon content.
11
Carbon
Manganese
Silicon
Sulphur
Phosphorus
Delhi Pillar
0.15%
0.05%
0.05%
0.005%
0.25%
Typical modern mild
steel (1015 grade)
0.15%
1.2%
0.3%
0.01% max
0.02% max
The level of impurities is generally low, typical
of ancient wrought iron, apart from the
phosphorus level which is over ten times that
of a modern steel. A high phosphorus iron ore
was clearly used and this element is present in
the iron. As a result, a very thin dark grey
protective layer of crystalline iron hydrogen
phosphate has formed on the surface of the
pillar. Subsequent amorphous (noncrystalline) rust forms which is compact, dense
and adherent with low porosity which is the reason for its resistance to corrosion. Any
crystalline rust that forms is porous, easily flakes off and does not contribute to protection.
Surely then we just need to increase the phosphorus content of steel to prevent it rusting?
Unfortunately, this amount of phosphorus has a detrimental effect on the mechanical
properties. While the Delhi pillar iron has quite a high yield strength typical of modern
structural steel, the phosphorus has greatly reduced the ductility as measured by
elongation. The impact toughness would be similarly reduced. A steel with such a high
phosphorus content would be far too brittle and suffer a problem that used to be known as
‘cold shortness’ (‘short’ is old term meaning brittle, as in short bread). It was recognised
many years ago that there needed to be limits on phosphorus in steel. In fact, the first
standard issued by ASTM in 1901, ASTM A1 for railway rails, included a limit on the
phosphorus content. A high phosphorus content doesn’t matter for a pillar that just needs
to sit there, but is totally unacceptable for anything that is going to be subject to stresses,
such as a bridge, building, rail or any mechanical device.
Yield strength
Tensile Strength
Elongation
Delhi Pillar
324 MPa
330 MPa
5%
Typical 350 MPa steel
345 MPa
450 MPa
25%
So, the ancient Indian blacksmiths (accidently) achieved rust-free iron 1600 years ago, but
unfortunately at the expense of useful mechanical properties. In the next instalment, we
will see how clever manipulation of the chemical composition can produce truly rust-free
steel as well as acceptable mechanical properties and has been used to produce one of the
modern wonders of architecture.
Matthew V. Veazey, “Materials Performance” 44(7) p16, July 2005
12
Chapter 7
A Stainless Steel Architectural Marvel
With the Delhi Pillar, improved corrosion resistance was achieved through alloy additions to
the iron, but this was the result of luck with the ore used. It was not until the late Victorian
era that scientific investigations produced the precursors to the modern corrosion-resistant
steels in use today. The discovery in 1882 of Hadfield’s manganese steel with its remarkable
wear-resisting properties probably started serious investigations into means of making
major improvements in steel properties by controlled additions of alloys. However,
attempts at improving the corrosion resistance of steel had commenced early in the
nineteenth century. Michael Faraday carried out experiments alloying iron with noble
metals such as platinum, although the results were disappointing.
Harry Brearley in
Sheffield is often
considered to be the
inventor of stainless
steel, but in fact there
were important
discoveries made
before he prepared
the first martensitic
stainless in 1913. In
Harry Brearly
Philip Monnartz
Eduard Mauer
1911, Philip Monnartz
in Germany discovered three important facts regarding stainless steel. Firstly, the
correlation between chromium content and corrosion resistance; secondly, that a significant
boost in corrosion resistance is achieved when the chromium content exceeds 10.5 per cent
and finally that molybdenum can have an importance influence on corrosion resistance.
Monnartz is also the first to use the term ‘passivity’ to describe the improvement in
corrosion resistance. Concurrently, Eduard Maurer and Benno Strauss at the Krupp works in
Germany alloyed steel with both chromium and nickel to produce the first austenitic
stainless steels. Others such as Elwood Haynes in America also claimed to have invented a
corrosion-resistant steel at around the same time. However, it was Brearley who recognised
the commercial significance of stainless steel and developed the large scale production of
the metal, initially for cutlery. In the early 1920s, a whole variety of chromium and nickel
combinations were tried with the best known being the18/8 or 304 stainless steel (18 per
cent chromium, 8 per cent nickel). The addition of nickel produced a stainless steel that was
more ductile, and more resistant to acid. Most of the standard grades produced in these
early years are still in use today.
13
The first major use of stainless steel in
architecture, an example that arguably has not
been surpassed, is the Chrysler Building, erected
in New York City in 1930. Walter Chrysler
engaged architect William Van Alen to design the
tallest building in the world, and at the same
time produce a building that would promote his
automobiles. A Krupp version of 18/8 stainless
known as ‘Nirosta’ was selected as the cladding
metal. It had gargoyles which were supposed to
represent Chrysler hood ornaments. The
stainless-clad radiating arched crown in a
sunburst pattern is the most impressive feature
of the Art Deco masterpiece. When the spire was
added in 1930, it was the tallest building in the
world, but less than a year later it was overtaken
by the nearby Empire State Building. The building
was declared a National Historic Landmark in
1976, and is often first in polls of architects,
engineers, historians and builders as their favourite building in New York.
A committee was set up to inspect the condition of the building every five years as there
was an obvious interest in the durability of stainless steel in architectural applications. This
committee was disbanded in 1960 because there had been virtually no deterioration of the
panels. The top of the building has been cleaned manually only twice, in 1961 and 1995.
During the 1995 cleaning, some dents and cracks were observed and repaired, and
superficial pitting near an incinerator vent was detected. But the condition of the stainless
was found to be excellent, looking like it had just been installed. As one commentator has
noted “With its stainless steel crown gleaming in the sun … the Chrysler building always
looks like the future.”
Of course, stainless steel is widely used in many applications other than architecture. PBS
reported in its television programme “The Streamliners”:
“Stainless steel, with its sleek, shiny surface and tremendous strength, is a marvel of
technology. It has revolutionized most modern industries, including food, medicine,
and transportation. … Stainless steel paved the way for modern technology and
continues to influence our lives every day.”
Alloying to make steel corrosion resistant was effective, but most applications required
something much cheaper. Therefore, putting a barrier between the steel and its
environment, a protective coating, has become the single most important means for
preventing corrosion. And, as we shall see in the next chapter, the most effective way is to
apply a thin layer of zinc to the steel.
Further reading: Harold M Cobb, “The History of Stainless Steel”, ASM International, (2010).
14
Chapter 8
The Unsung Building Material
Corrugated iron is a widely-used building material whose importance is rarely
acknowledged. It is used in all climates, all terrains, cheap, easily fabricated into all sorts of
buildings and can probably claim to shelter more people from the elements than any other
building material. Corrugated iron, often incorrectly called ‘tin’, is usually coated with zinc
so terms such as ‘corrugated galvanized iron, ‘galvanized iron’ or even ‘galvo’ are often
used. But like all great inventions, it has evolved over time so we now have coatings such as
zinc-aluminium, zinc-aluminium-magnesium along with special durable organic coatings
providing a wide range of colours. The durability of the new products has improved so much
that it is the fasteners, not the sheeting, that often break down first. But regardless of the
coating, this simple material made of a thin sheet of steel, crinkled for strength and rigidity,
then provided with a suitable protective coating, has contributed to development of
farming, light industry, housing and many other fields of human endeavour like no other
building material.
Today, corrugated metal sheets are made by a roll-forming process where wavy rolls press
the sheets to give the desired corrugations. The sheets are then cut to the desired length.
Rolling and coating is now a completely mechanised process. The corrugations provide
greatly increased stiffness and rigidity compared to flat sheets along their length, but also
give the ability to be shaped into curved forms. The pitch or distance between corrugations
determines the strength, with lowest pitch (‘ripple iron’) having the lowest strength and
generally only used for internal applications. A number of new profiles have been
introduced in recent years providing a range or architectural options.
15
The first patent for ‘indented or corrugated
metallic sheets’ was granted to Henry
Palmer of the London Dock Company in
1829. The company purchased flat wrought
iron sheet, rolled it to shape using fluted
rollers and a year later the first building
roofed with this material was constructed
at the London docks. The roofing was an
immediate success and railway stations,
markets and other large span enclosures in
England were soon roofed. These first
examples were protected with a thin layer of paint, which provided limited protection from
corrosive smoke, steam and salt air. The problem was addressed by Stanislaus Sorrel, a
French civil engineer, who in 1837 patented a process of coating iron with a thin coat of
zinc, although the sheeting was still often painted for decorative purposes.
By the 1850s, mass production and increased competition led to more widespread use of
the material. The gold rushes in California and Australia in the 1850s led to a market in prefabricated buildings that would be light weight and quick and easy to erect and corrugated
iron formed the basis of the first flat-pack industry. Even after the gold rushes subsided,
corrugated iron remained an ideal building material in remote areas and by the outbreak of
the First World War, it was a common feature of rural landscapes around the world. But it
was also widely used in built-up regions in domestic, commercial and industrial applications.
By this time, steel had replaced wrought iron as the base material and it had become
cheaper. War brought perhaps the most famous corrugated iron building, the semi-circular
Nissen hut and its American version, the Quonset hut, where the lightness, ease of transport
and erection made them a great success with the military forces. In recent years, the
product has managed to shake off its rather utilitarian image through the work of a number
of imaginative architects who have used it to produce buildings of elegance and style which
fit in well with the local landscape.
If corrugated iron has been
important in the developed
West, then it is almost a
currency in the developing
world. Since the Second
World War, informal
communities with populations
of a few hundred to a million
or so have sprung up on the
periphery of urban centres in
Africa, Latin America and
south Asia. Without land title
or money, the residents have
adopted corrugated metal as
a flexible, cheap and easy to work with building material. It is suited to hot and temperate
16
climates; it can withstand monsoon rains and is rot-proof. It can be easily erected and pulled
down and when no longer needed for housing, it can be used for channelling water,
covering muddy paths or an animal enclosure. As David Egerton has remarked:
“Cheap, light and portable, [corrugated iron] is one of the great technologies of
poverty, together with the T-shirt and the flip-flop.”
How Zinc Protects Steel
Coating steel with zinc is perhaps the most
important means of protecting steel. It will
provide barrier protection while intact as its
corrosion rate is much less than that of steel.
But more importantly, if there is a pinhole or
damage to the zinc coating, then the zinc
corrodes in preference to the steel providing
sacrificial protection, and we say that the
steel is galvanically protected by the zinc.
The zinc can be applied by a number of
methods apart from dipping in molten zinc, such as electroplating and thermal spray. Zinc powder
can be dispersed in a paint binder to form a zinc-rich paint. The protection given by the zinc depends
on the coating thickness, with greater protection given by thicker coatings. The environment is also
important, and coating life diminishes as the environment becomes more corrosive.
Corrugated iron has been and continues to be an invaluable building material that deserves
to be taken seriously. It shows that steel can be simply and cheaply formed to a useful
shape, protected from corrosion by a range of coatings, and made accessible to citizens in
all corners of the globe. But for heavy steel sections in severe environments, other coatings
such as inorganic zinc silicate, discussed in the next chapter, are needed.
Further reading: Adam Mornement & Simon Holloway, “Corrugated Iron”, Frances Lincoln
Ltd, (2007).
David Egerton, “The Shock of the Old; Technology and global history since 1900” (Profile Books 2006).
17
Chapter 9
Zinc Silicate: Liquid Rock for Years of Protection
At the outbreak of the Second World War, the Australian government decided to build a
blast furnace and shipyard near the then main source of iron ore at Whyalla in South
Australia. However, as this site was on the edge of a desert, fresh water needed to be piped
360 kilometres from Morgan on the Murray River. An above-ground welded steel pipe was
proposed and the local Water Authority, responsible for the project, considered possible
coatings. After investigation of possibilities available at that time, they decided that ‘nothing
could hold a candle’ to the newly developed inorganic zinc silicate. At this time, most steel
was protected with oil-based coatings which needed re-application every few years. Their
faith was vindicated as the original coating, shown in the photograph near the Whyalla
steelworks, is still largely intact over 70 years later. In fact, inorganic zinc silicate either
alone or part of a coating system, now probably protects more steel from the ravages of
corrosion than any other single protective coating apart from galvanizing.
Inorganic zinc was developed by an Australian inventor working in his shed in suburban
Melbourne. Victor Nightingall (1881-1947) had many interests including agriculture, electric
heating and x-rays and had taken out a number of patents. In the 1930s he decided to try to
develop a totally new type of protective coating by reacting sodium silicate (like a liquid
glass) with zinc powder and applying it to a steel surface. He was hoping that the
components would react together to form an iron-zinc-silicate mineral rather like a mixture
of the minerals Williamite and Franklinite. We know now that the extent of reaction was
18
restricted to the surface of the iron and zinc particles, but after
much experimentation he came up with a successful coating that
clearly provided superior protection than any other product on
the market. He coined the term ‘dimetallization’ to describe the
reaction between the zinc and iron, and formed the Dimet
Company to market the product. The coating required heating to
cure it to sufficient hardness, but it was used successfully on a
small number of projects in Melbourne before being adopted for
the Morgan-Whyalla pipeline. After the war, it was adopted for
other similar pipeline projects around Australia and became
widely used for other applications where the stoving process
was not an issue.
In 1949, Charles ‘Chuck’ Munger of the Ameron Company visited Australia to inspect the
Morgan-Whyalla coating, and other similar projects. He was impressed and licensed the
product for use in the United States, where it was marketed as Dimetcote. The stoving
process was, of course, a severe limitation and work by Ameron and in Australia developed
a post-cured product where a curing agent was washed onto the coating after application.
By the 1960’s, self-curing water-borne products were available, soon followed by solventborne products, simplifying application even further. These are the products in use today
and are marketed by most large paint companies around the world.
Inorganic zinc silicates are widely
used for steel structures where the
grey colour is acceptable, such as
road bridges as shown left. They are
remarkable coatings and unlike
other paints in many ways. Being
inorganic, they are unaffected by
sunlight, ultra-violet radiation, rain,
dew, bacteria, fungi or
temperatures up to about 400°C. If
they are damaged or worn away,
the zinc continues to provide
galvanic protection to the
underlying steel and porosity in the coating is filled with corrosion products. As the zinc is
further consumed, rust may start forming but will not grow under the intact zinc coating,
unlike normal paints. They resist most organic solvents and have excellent friction
characteristics. In fact, they are usually the only paint coating allowed when structures
contain friction-grip joints. Most importantly, a properly applied single coat of inorganic zinc
will give excellent protection to steel for years or indeed decades, even in some quite
aggressive environments. They are truly unique and it is little wonder that they have
revolutionised the means of protecting steel structures from corrosion.
19
Chapter 10
Ever-present Epoxy Coatings
If you work in corrosion control, you will undoubtedly come across epoxy coatings. They are
used wherever steel has to be protected against corrosion – offshore platforms, onshore oil
and gas production, refineries, petrochemical plants, power plants, bridges, ships, wharfs
and many more. They will protect steel in the atmosphere from rusting by preventing
oxygen and water reaching the surface. They will prevent the interior of steel tanks from
reacting with cold water, hot water, petroleum and other organic products and many other
acidic, alkaline and pH neutral chemicals. For good measure, they are also used to protect
other surfaces such as concrete and non-ferrous metals. If you had to name the most
versatile method of preventing corrosion, an epoxy coating would be a good choice.
So, what is it that makes epoxy such a useful chemical? The term epoxy refers to
thermosetting polymers (one that cures irreversibly by molecules cross-linking) produced by
reaction of an epoxide group (often also confusingly called an epoxy group), which is a
three-membered ring of an oxygen atom attached to two adjacent carbon atoms. The ring
structure of the epoxide group is easily opened and provides a site for crosslinking to form
the final polymer. The epoxide group is on a small molecule, most commonly
epichlorohydrin (ECH) which is reacted with a much
larger molecule containing lots of carbon ring (aromatic)
and chain (aliphatic) structures, most commonly
bisphenol-A (BPA) to form what is known as an “epoxy
prepolymer”. This is a large polymer molecule, but still a
liquid, and forms the resin half of the final product. It
needs to react with a hardener (also called a converter) to cure to form the final, highly
crosslinked product that is strong, hard and provides the required corrosion resistance. No
volatiles are given off during cure so shrinkage is much less than for other polymers.
One common hardener is polyamine or, simply amine, which is an organic molecule
containing nitrogen and hydrogen atoms rather like ammonia. The hydrogen atoms on the
amine react with the oxygen atoms on the epoxy prepolymer to form the three-dimensional
cross-linked polymer that gives the final product its excellent properties. The polymer has
many charged molecular groups such as hydroxides which make it polar and ensure good
adhesion to metallic surfaces. Furthermore, the carbon-carbon and other linkages along the
polymer chain are strong and very stable giving epoxies their good chemical resistance,
strength and toughness. At the same time, cross-linking is just sufficient enough to give the
film some flexibility.
There are a range of epoxy types depending on the resin or hardener used making epoxies
one of the most versatile polymers. Other resins than BPA include bisphenol F and novolac
which have improved resistance to certain chemicals. As well as amine, another common
hardener is polyamide, which has lower shrinkage on curing, increases the flexibility of the
20
film and gives a longer pot life, but has reduced chemical resistance. There are different
formulations for different applications. For atmospheric coating systems, a polyamide
hardener is generally used, and there are pigmented and non-pigmented primers and
intermediate coats. The major weakness of epoxies exposed to the atmosphere is that they
chalk due to reaction with UV, so they not used as topcoats where colour or gloss are
important, although chalking has only a minor effect on durability. For maintenance work
where abrasive blasting is often not possible, surface tolerant epoxies (or epoxy mastics)
which are formulated to soak into poorly prepared surfaces as well as dry slowly are the
usual primer of choice. For more aggressive environments such as splash zones, very high
build or ultra-high build epoxies are often specified. For tank linings, solventless epoxies
with or without glass reinforcement, are ideal. For pipelines, powder coatings (fusion
bonded epoxies) are used alone or as part of a three layer system. Various additives and
modifications can create products for high temperatures, wear and abrasion resistance, fire
resistance and non-slip flooring. It is not surprising that most corrosion control activities will
use epoxy coatings at some stage.
Epoxy coatings are widely used for tank floors, piling and reaction vessels
The first true commercial bisphenol epoxy resins were
discovered in the late 1930s by Pierre Castan (1899 – 1985),
pictured, working in Switzerland for the company that
eventually became Ciba-Geigy. He was attempting to find a
product which could be used for dentures, but this was not
commercially successful. At around the same time, Sylvan
Greelee working for the Devoe-Raynolds in the USA was reacting
bisphenol-A with fatty acids to produce an air drying coating.
Various chemical companies developed this original research
after World War 2 and commercial epoxy resins for coatings
made their debut in the late 1940s. Protective coatings were
one of the first and are still the most important application of epoxies accounting for around
50% of all epoxy resins produced, but epoxies are also found in adhesives, castings, flooring
and many other uses.
21
Chapter 11
Boilers, Steam and Water Treatment
It is difficult for us in the 21st century to imagine some of the hazards and dangers that were
associated with the Industrial Revolution as it spread across the developed world two
hundred years ago. It was steam that drove the revolution with boilers providing the energy
for the locomotives and steam ships, as well as the stationary engines that ran the factories.
But the rapid development of steam power brought many disasters. In 1815 in northern
England, an experimental railway blew up killing 16 spectators. The boiler in the steampacket “Union” exploded in the English port of Hull in 1837, killing 20 and injuring the same
number. But it was in the USA that boiler accidents were most common and tragic. The
boiler in a printing press and machine shop in Hague Street, Manhattan exploded in 1850
killing 67 and injuring 50. In April 1865, the boiler in the paddle steamer “Sultana” blew up
with an estimated cost of 1500 lives, more than the loss on the Titanic. Railway boilers often
suffered catastrophic explosions, as shown in the photograph. Between 1880 and 1890
there were over 2000 boiler explosions in the USA alone.
There were many reasons for these and other similar disasters. Boilers were originally made
by riveting together small sheets of wrought iron. Its strength was adequate for the
relatively low pressures in the early days, but the higher boiler pressures necessary for
larger trains, ships and stationary engines required stronger materials which were not
available or too expensive. Operating guidelines were unknown, steam pressures were
regularly increased beyond a safe level (safety valves were unreliable and frequently
screwed down) and inspections were rare. Corrosion, cracking and problems arising from
scaling and fouling were not the most important boiler problems, but there is no doubt that
22
the attention given to these from the late 1800s on was an important step in improving
boiler safety. Understanding and dealing with the corrosive and scaling properties of water
so that boilers could be safely and efficiently operated, was an important technological
development that has largely been overlooked.
As steam is produced in a boiler, the impurities
left in the feed water concentrate and they
precipitate out of the solution and onto the
internal surfaces of the boiler causing fouling,
generally known as incrustation in the 1800s.
This reduces both the water flow and the heat
transfer decreasing the efficiency and power of
the boiler. Such fouling can accelerate
corrosion of the boiler, decreasing its life.
Impurities can also cause foaming from bubbles
which burst as steam is generated also
degrading boiler operation. Corrosion was
considered less of a problem than fouling as
boilers often had a very limited life of five years
or so, but became increasingly important as
boilers became more complex and scaling
problems diminished. For marine steamships,
salt water was used in the boiler until the mid1850s, and the incrustation it produced
required continual cleaning. Steam locomotives
exhausted to the atmosphere so water had to be constantly replenished. Over the course of
a route, considerable variations in water quality were found creating different types of
incrustation. The problems were less with land boilers as the feed water was constantly
recycled.
Rather than attempting to treat the water in the first place to prevent fouling arising as we
would do these days, the problems were initially dealt with by regular cleaning of the boiler.
Removing scale was a slow and arduous process, and numerous means were found to make
it easier. These methods were discovered serendipitously or by trial and error. The table
from Molesworth’s Pocket Book of Engineering Formulae of 1888 gives some incrustation
removal methods that were adopted with more or less success. For example, in what would
appear to us the strangest solution, it was found that boiling potatoes in the boiler water
(Item 1) made scale removal easier. Apparently, the starch in the potatoes caused a soft
sludge rather than a hard scale to form. Tannins and lignin from wood, plant matter and
other organic sources described in items 2, 3, 7, 8 and 11 had a similar effect by forming a
soft sludge. Tannin had other advantages such as removing oxygen and is still used today in
some water treatment systems. It does react with iron, especially under neutral or acidic
conditions, and its use needs to be carefully monitored as noted in item 7. Molasses (item 6)
also forms a soluble compound with calcium salts, making sludge removal easier. Keeping
the water slightly alkaline (items 2, 4 and 9) is still standard practice for water treatment to
minimize corrosion risk. Phosphate is another treatment used in the early days which is still
23
in use today. Frequent blowing off (Item
12) to replace contaminated water with
fresh water is also a common method of
water treatment. It is interesting to note
that around this time, although not
mentioned by Molesworth, cathodic
protection using zinc plates was
recommended by some sources,
although they recognized that regular
replacement was necessary due to the
high corrosion rate of zinc in hot water.
From the late nineteenth century, the
higher powered boilers in use had
condensers and pure water could be
used initially and reused, with only a
small amount of makeup water
required. An understanding of the
chemistry and corrosion properties of
water was also developing at this time
and these principles were applied to
boiler water. The importance of keeping
the water as pure as possible and of
minimizing oxygen content was passed
on to boiler operators. However, the
idea that additives could be beneficial
was still some way off.
Additives were introduced in the 1920s, when steam locomotives were dosed with enough
caustic soda to make the water slightly alkaline to reduce the risk of acid corrosion but close
enough to neutral to minimize scaling. By the 1930s, it was realized that adding other
appropriate chemicals to the feed water meant these problems could be avoided in the first
place. Appropriate corrosion and scale inhibitors were developed and widely used for
treating boiler water. Other industrial waters, such as cooling water for heat exchangers,
were treated on a more scientific basis at about the same time. As with boiler water, scale
was the main enemy and similar treatments to boiler water - use of soft water, slight
alkalinity, tannin and regular blow down - were the main treatments. Development of the
first scaling index by Langelier in the 1930s further expanded scientific understanding of the
fundamentals. Over the next decades, investigations into scaling and corrosion processes,
along with the “new “problem of biological fouling, brought new products and practices in
use today to control the often conflicting requirements to prevent corrosion, scaling and
fouling.
24
Chapter 12
The Birth of Corrosion Science
Not far from Piccadilly Circus in London’s West End, stands the impressive Royal Institution
building, opened in 1799 for the advancement of science. In this building, two of the most
eminent scientists of the nineteenth century made significant contributions to corrosion
science and technology, including work on the fundamentals of galvanic corrosion, discovery
of cathodic protection and creation of the terminology for corrosion reactions still in use
today.
Right from the start, the Royal Institution considered it important to reach out to the
general public to show the importance of science in all works of life. It employed the young
chemist Humphry Davy (1778-1829) in 1801 to stage entertaining and spectacular
demonstrations of science in public lectures. These became one of the most popular events
in London, and Albemarle Street became its first one way street. Davy also established a
laboratory for scientific research and received a knighthood for his invention of the miner’s
safety lamp. But less well known were his researches into
electrochemistry. Following Galvani’s discovery of galvanic action
in Bologna, Italy in 1780 and Volta’s invention of the electric
battery in the late 1790s, Davy set about building the largest
battery in the world at that time with 2000 pairs of plates. Using
this, he managed to isolate elements such as sodium, potassium,
calcium and other reactive elements for the first time. He
showed there was a relationship between chemical reactivity and
electricity, and produced what is probably the first Galvanic
Series, which he described as “the different substances are
arranged according to the order of their known galvanic powers,
25
[and] will shew [sic] how intimately chemical agencies are related to the production of
galvanism.”
Davy recognised the
importance of dissimilar
metals in corrosion
behaviour: “Iron nails soon
wear out when used to
attach copper sheeting to
ships and iron pins
employed to attach lead to
roofs of buildings rust with
great rapidity, which is
owing to chemical
operations being increased
by the electrical energy of
contact.” He was asked to look at the corrosion of copper cladding used to prevent worms
attacking the hulls of wooden naval ships. In 1824, Davy found that attaching iron or zinc
‘protectors’ prevented copper corrosion, pioneering cathodic protection. Unfortunately, this
major discovery was a practical failure because copper needs to corrode to prevent
formation of marine growth. But Davy can be considered as the father of cathodic
protection, and an important pioneer in understanding of corrosion.
Davy’s successor at the Royal Institution became an
even more famous scientist. Michael Faraday
(1791-1868) is rightly remembered for his
discoveries in electro-magnetism leading to
development of the electric motor and electric
generator. But Faraday also carried out work in
electro-chemistry, initially as assistant to Sir
Humphrey Davy. His most important discovery in
this area was his eponymous laws of electrolysis
which showed the relationship between current
and amount of metal corroded. It is ironic that the
most useful mathematical formula in corrosion
science was discovered by Faraday, as he had left
school at age twelve and was always self-conscious
about his lack of mathematical prowess. He made
other contributions. After discussions with
Cambridge polymath, William Whewell, he coined
the nomenclature of electro-chemistry with which we are familiar today (electrode, anode,
cathode, ion, anion, cation, electrolysis and electrolyte). In 1836, he carried out experiments
on iron passivity, noting that iron placed in concentrated nitric acid did not corrode while
rapid dissolution was observed in dilute nitric acid.
26
Faraday is also probably the first to suggest the combined use of protective coatings and
cathodic protection for marine structures, a technique widely used today, when asked for
advice on protecting iron piles for lighthouses:
“Though iron be a body very subject to the action of sea water, it does seem … that it
may be used to advantage in marine constructions intended to be permanent,
especially if the joint effects of preserving coats and voltaic protectors were
applied.”
The Royal Institution is a worthy place to conclude this series as it brings us back to the most
corrosion resistant metal – iridium – discussed in the first article. According to the Royal
Society of Chemistry, Smithson Tennant, the discoverer of iridium in 1803, announced his
finding … at the Royal Institution.
27
Tales of Metal Resilience – Robert A Francis
An iron dagger found in Tutankhamun’s tomb. A water pipeline in the Australian outback. An
ancient iron pillar outside India’s capital. An art deco architectural masterpiece in New York.
What do these disparate items have in common? They are all examples showing it is possible
to prevent corrosion which destroys tonnes of metal around the world. This publication
provides twelve short vignettes covering these and other instances of metal resilience –
victories in our long-standing fight against the ravages of corrosion. These examples are
from around the world (and beyond) and from the distant past as well as present. It is
designed to show that corrosion can be defeated and that corrosion science and engineering
is as interesting, historic and artistic as any other.
Rob Francis is recently retired corrosion and coating consultant with 50 years’
academic, industrial and consulting experience in corrosion and protective
coatings. Dr Francis has a B.Sc. in metallurgy and a Ph.D. in corrosion science. He
has authored or co-authored over forty technical papers or presentations on
corrosion and coatings. He is also active on a number of standards committees in
Australia and overseas.