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Some perceptions of corrosion and its control
Telling the Truth and Nothing But the Truth
Peter Elliott, Corrosion & Materials Consultancy, Inc., Las Vegas, USA.
This is the first in an occasional column, to inspire new graduates into working within our industry, by highlighting the interesting and varied aspects of a career in corrosion control, as experienced by members of the institute.
Times change, as does the understanding of corrosion and its control. As a graduating metallurgist with interests in high temperature oxidation and corrosion, my first research job, with Imperial Metal Industries, Birmingham, was the challenge of developing a metal, actually a refractory metal alloy containing tantalum, hafnium and niobium, that could survive a round trip into space. Using a high-temperature glaze from the Potteries as a coating – it worked. My interests were further enhanced by attendance at a local Institute branch meeting on corrosion by Professor T.K. (Ken) Ross, a chemical engineer, who enticed me to leave the space race and join him at what was then the University of Manchester Institute of Science and Technology (UMIST). He invited me to conduct research and asked if I knew anything about boilers. To my surprise, when I replied “no”, he replied “Perfect, I want someone with an open mind. Come and join us. When can you start?”
The return to my hometown of Manchester, to a Chemical Engineering Department, which in 1968, witnessed the creation of the Corrosion and Protection Centre – the first such academic department in the world to focus on teaching, research and industrial consulting services addressing corrosion and its control. Joining the UMIST staff my interest in boilers grew, but, by noting that metals don’t always stay hot, so did my knowledge in aqueous corrosion,including the measurement of atmospheric corrosion, which was particularly valuable – see below.
For countless years perceptions about corrosion have suggested that this often visually alarming disease is unsurmountable. Corrosion cost surveys proclaimed enormous financial losses, classed as high percentages of the Gross National (or Gross Domestic) Profit. Akin to cancer and other diseases, there are parallels with corrosion control, where advances in monitoring, understanding, and treating causes with palliative cures, has grown significantly. Over the years I have noted parallels to the UK National Health Service that operates more as a National Disease Service, where exercise and healthy foods were lacking, medicines were not taken, examinations were not performed, and surgery or continued hospitalisation was required. A better understanding of corrosion, promulgated by professional societies, at least recognising (better still understanding), the interplay of thermodynamics [can a material react?] and kinetics [how fast can it be ?]. Those who seek young, experienced chemists, engineers, and metallurgists, are apparently ignorant to this oxymoron; age hardening (misquoted) reflects years of experience along with expertise.
I have continued my interest in corrosion failures – from establishing a museum in what was the UMIST Corrosion & Protection Centre so many years ago, to sharing examples at countlessmeetings and in publications. I am particularly fascinated by unusual cases, for example a case that revealed a “crack” is not a crack, which brings
back memories of Turner’s Laws of Corrosion, e.g., “Nor all
that be cracked, needeth it be SCC”.
The case in question pertains to a leak in the top of a ¾”- diameter domestic cold-water pipe, which after 21 years’ service, was first attributed to a lateral crack (Figure 1A), until laboratory examination showed a complex pattern of localised pitting from the inside of the pipe (Figure 1B). The cause was apparent when the farmhouse homeowner shared the history of his convenient (for him) but unusual water sources, comprising of two years “dirty” well water, followed by 20 years of soft rainwater collected from the roof of his building. These uniquely different conditions favoured localised pitting, which progressed with sustained attack from the soft water that ultimately fully penetrated through the top of the copper pipe as the pinhole leak. The copper was not defective; there was no evidence of stress corrosion cracking.
To date, with over two million airline miles and many thousand traveled by road, my response to the question “what have you learned most?” is my knowledge of geography! In a recent litigation matter an opposing expert stated that my report was biased. A few months later – when monitored atmospheric data was available – truth prevailed. The settlement was enhanced as the bias was refuted. Telling the truth is the key to corrosion control.
1. Hoar report (UK), NIST, Library of Congress (USA)
2 P. Elliott, Gallery of Corrosion Damage”, Metals Handbook, 13B, ASM International, p.629-646, 2005.
3 M. E. D. Turner (Mervyn) – deceased – private communication.
Fig 1A “Crack” in top of ¾”diameter copper pipe.
Detail of “crack.”
OD top pf pipe.
Close to “crack” location.