Fred Starr recollects: Brief Encounter

Materials World magazine
20 Jan 2017

Fred Starr recollects…

What looks like a cross section of a volcano is, in fact, another facet of a rather odd form of high temperature attack – metal dusting, where the corrosion product is a dust. But my efforts to discuss it, at a workshop in Frankfurt, Germany in 1997 were, in my opinion, sabotaged from the start and undermined throughout.

The ‘volcano’ is the result of attack at a tiny spot on the metal surface, where the voluminous metal dust has peeled it back. The dust consists of particles of alloy, metal carbides and filamentary carbon. British Gas (BG) met the problem in the mid-1960s in quite an embarrassing way during its development of a gasification process, where hydrogen reacted with oil to give a methane-rich gas. Doping the hydrogen with sulphur did away with the problem. But I was only allowed to describe these happenings years later, in 1979 at an Institute of Metals conference in the Isle of Man. I was hesitant in making the presentation, as the metal dusting work had been done by another part of BG research, before my time. However, it provided a basis for the rest of the paper, where I announced our unique approach to developing corrosion-resistant alloys.

No one ever followed up the insights into metal dusting. The cynic in me supposes that if the BG solution had proved generally applicable, it would have ended a generation of well-funded PhDs and Professorships. More objectively, our process involved environments quite different to standard experiments. These involved high-purity synthesis gas containing CO and H2 and could be done in the lab. Ours involved methane and hydrogen at 30 bar pressure at 750°C. The equipment was expensive to build, run and maintain.

Metal dusting is weird, with the real action going on at the atomic scale, beyond even the reach of electron microscopes. The mechanism can only be inferred. By the mid-1990s, it seemed to me that nothing much new had been determined about possible mechanisms. The same sort of experiments with mixtures of CO and H2 were being endlessly repeated. So when I heard about Frankfurt, I offered a rehash of the Isle of Man presentation – it would be new to most people. In my innocence, I thought a different, plant-based experience would be welcomed. But it wasn’t by the workshop Chairman, an internationally recognised expert on the subject.

The stance I took was that metal dusting involved a catalytic step, and was inhibited by a few ppm of H2S. This was contrary to the accepted view, whereby a metastable carbide formed first, then broke down into graphite and more stable carbides. But that didn’t account for what happened to us, where, even in the absence of metal dusting, heat exchanger tubing could carburise until it was as brittle as pottery.

My presentation was the first on the final day, the sabotage beginning the night before with a well lubricated conference dinner. At my starting time, most of the somewhat hungover delegates were still checking out of the hotel. I delayed as long as possible, but eventually had to begin. Every so often, a new group of delegates would bang open the conference room doors, laden with suitcases, fighting their way to the seats.

I struggled on. Then, to my amazement, the Chairman got up to interrupt, lambasting me about where I was wrong. No attempt was made to concede I was coming from a different angle. Running out of time, I never got to present the non-metallurgical evidence. We crossed swords only once – on that, for me, memorable occasion. Later on, I came to realise his interjections were quite predictable, him taking no prisoners. Another time, a quick witted Australian Professor congratulated him for ‘giving the conference two lectures for the price of one!’

If science is to advance, it needs theories. Zealots and disciples will rally to the cause, creating a well-crafted system of beliefs, principles and predictions. But there needs to be, especially in metallurgy, a place for the agnostic – usually misguided, but occasionally prescient, pointing to the need for more enlightening experiments or refined equipment. Metal dusting, I suspect, still awaits that real breakthrough.