The Effect of Electrolyte Properties on the Mechanism of Crevice Corrosion in Pure Iron

Abstract

The roles of applied potential, solution resistance, pH, and temperature on passive and active metal dissolution and hydrogen evolution inside crevices were evaluated using in situ measurements of potential distribution, pH, and other data, for systems with active/passive transitions in their polarization curves. Their roles can be explained in terms of a requisite IR voltage drop, Δϕ*, for active metal dissolution to occur inside the crevice: IR > Δϕ*. Accordingly, crevice corrosion was suppressed in the systems studied by: (i) increased pH (or deacidification) of the crevice solution (the increased Δϕ* and decreased I dominated over the increased R), (ii) increased solution conductivity (decreased R), (iii) decreased solution temperature (the increased Δϕ* and decreased I dominated over the increased R), and (iv) a more noble applied or corrosion potential in the passive region (increased Δϕ*). A decrease in oxidant availability during open‐circuit corrosion reduces the susceptibility by decreasing I.