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A Rant.

Corrosion Monitoring.

On a shelf next to my desk sits an old sealed plastic juice jar containing three IKEA teaspoons - the worst stainless steel imaginable - in some acidified salty glop. Connected to the three teaspoons is a prototype electronic corrosion coupon. Built by Pepperl+Fuchs, it comprises the innards of their now discontinued CorrTran MV, plus a real time clock and a USB memory stick interface. It is powered by an old 5V power supply, but would happily run for a year on a pair of AA batteries. It is not a finished product, the pair of small circuit boards have some hand-soldered jump wires and the firmware could do with a tweak or two. But it runs.

Every hour, for the past eight odd years, the thing wakes up, takes a corrosion rate reading and turns itself off again. When I remember, I plug in a memory stick, push a button and dump out the data - a text file with time stamped corrosion rate - measured using potentiostatically applied harmonic distortion analysis, conductivity between the probe elements, Stern-Geary B value, electrochemical noise pitting factor and a few columns of diagnostic data such as electrode offset voltages, error codes and so on. There is enough space on the 1 gig memory stick to last just about forever.

The IKEA teaspoons are happily corroding at some quite low rate, occassionally bursting into a spell of pitting corrosion.

A useful device, one would have thought. No cabling required for installation, just pop round once a year to change the batteries and suck out the data. Just the sort of thing to put on a pipeline in the middle of nowhere or in some rarely visited plant location. Should be selling like hot cakes.

Not so. The project petered out, never got past having a batch of prototypes made and ended up in the dustbin of history.

It took me a while to figure out why. The reason is that no-one actually wants reliable corrosion rate monitoring. What people want is something that tells them that their plant or whatever is not corroding. The last thing the operators want is a device which shows that most of corrosion happens over relatively short periods of time, when someone screws up and puts something that shouldn't be there down that pipe or into that tank. Conventional weight loss corrosion coupons conveniently average corrosion rate over months or years. No-one really wants a device which accurately measures and records corrosion rate in real time, making it hard to hide any cock-ups.

So, there is no future in electrochemical corrosion monitoring. It was fun though, while it lasted.

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