Don’t Believe Everything You Hear - The 22nd William Blum Lecture
This article is a re-publication of the 22nd William Blum Lecture, presented at the 68th AES Annual Convention in Boston, Massachusetts, on June 29, 1981.
Dr. Joseph Edwards
Manager, Electrochemistry Research Group
International Nickel Company
Birmingham, England, U.K.
Recipient of the 1980 William Blum AES Scientific Achievement Award
Originally published as Plating & Surface Finishing, 68 (9), 59-64 (1981)
Editor’s Note: This article is a re-publication of the 22nd William Blum Lecture, presented at the 68th AES Annual Convention in Boston, Massachusetts, on June 29, 1981. A printable PDF version is available by clicking HERE.
Dr. Edwards offered these opening remarks before delivering his William Blum Lecture:
“I have had a year to get used to the idea, so it may be difficult for me now to recall to you the pleasure and astonishment I felt at being honored with the AES Scientific Achievement Award. It was like dreaming that Britain had put a man in space, and waking to find it was me. It was an eventuality I had never contemplated, yet I know the award well. I have met nearly all the previous recipients and regard some of them as particular friends. It is a great honor to be accorded membership in such a select club.
"Not long ago I saw a cartoon by W. Hamilton showing two men in the prime of life, financially speaking, holding a conversation. One was saying to the other, 'I have learned a lot in 63 years. But, unfortunately, almost all of it is about aluminum.' With me, it's not aluminum (or even aluminium, as we call it), but I do see his point. In any case, on this occasion, technology is our common ground and technical reminiscence will have to provide my material.
"I needed a theme, and so I chose as my text, 'Don't believe everything you hear.' In many contexts this is advice no one needs - in buying a second-hand car or in reading the paper. There is no better test of this than to talk to a reporter and force yourself to read his article when it appears. It gets you in the pit of the stomach. Much the same feeling as when you discover you have reversed the car over the cat. The feeling passes ... the cat escapes, the article is soon forgotten. In fairness to the journalist, his needs are different from ours. He must capture attention. He has to meet his deadline. Hence his motto: 'Don't get it right, get it written.'
"So, don't believe everything you hear. Let us see how that applies in a technological context."
I’ll begin with my first electrochemical investigation. I was looking at electropolishing, a process by which a rough, dull metal surface is made smoother and brighter by anodic dissolution. There was no satisfactory explanation of the phenomenon. It was known that polishing did not begin until a little while after the circuit was closed, at a point where the current fell sharply. It was stated that at this point the current density fell more steeply on recessed areas than on projecting areas of the surface, so that current distribution subsequently favored rapid removal of the projections.
It seemed a good idea to demonstrate this change experimentally, so I made an electrode on which I could measure separately the currents on peaks and recesses. It comprised a stack of about 40 copper sheets, each insulated from its neighbor, with alternate sheets connected together in two sets. One edge of the stack was exposed, and this constituted the anode surface.
Part of the surface is shown in Fig. l(a). One set of foils was made anodic in phosphoric acid solution and partially dissolved to give a surface of alternating ridges and grooves (Fig. l(b)). Because the insulation had swelled, it was trimmed back under a microscope, to look like Fig. l(c) or (d). The profile in Fig. 1(d) proved the more satisfactory because it was more stable. It meant that the area of the ridge was now greater than that of the grooves, but this was not important. The ridges would take a higher current, anyway. The question to be answered was how far the ratio of current between ridges and grooves would change when polishing conditions were established.