Shin-ichi Motoda

The effect of marine fouling on the ennoblement of electrode potential for stainless steels

Abstract Electrode potentials for 18 kinds of stainless steels and commercially pure titanium were measured in live sea water pumped up into the laboratory room through a 100m-long pipe, so that the specimens were fouled by only the brown slime. After 10 days of immersion, the electrode potentials for all the specimens attained to about 400mV(SCE). Deposited slime was examined under a scanning electron microscope and analyzed in terms of fluorescence. It was found that the slime was composed of living sea diatoms. Variations of electrode potential for stainless steel which had been immersed for 35 days were measured with successive removal of the deposited layer. The electrode potential remained noble after removal of the slime layer, while it decreased drastically after subsequent removal of a thin organic film under the slime layer. The ennoblement of the electrode potential is caused not by the metabolism but by the metabolite of the sea diatoms included in the thin organic film.