Clarification of Dynamic Corrosion Behavior and Electrochemical Approach to Corrosive Wear Mechanism

We have investigated the corrosion behavior under sliding condition。Such condition is referred as dynamic corrosion，because on the surface suffered sliding friction fresh surface is exposed continuously and the corrosion behavior is quite different from ordinal corrosion，I.e.，static corrosion.The electrochemical approach is very effective to understand the corrosive or electrochemical factor contributing corrosive wear。However，corrosive factor is determined by the product of area of the fresh surface exposed and corrosion current density of the fresh surface。Unfortunately both parameters are unknown.We assumed that the corrosion current density was estimated from the current density obtained by potential pulse method(PP Method)。Wear experiment was carried out in Na Ii D22 IeD2SO Ii D24 IeD2solution for SUS304 stainless steel，pure iron，pure copper，6-4Brass，pure aluminum and zirconium alloy(zircaloy-4)under free potential and controlled potentials.This evaluation method was quite good for wear free d24ii solution for SUS304 stainless steel，pure iron，pure copper，6-4Brass，pure aluminum and zirconium alloy(zircaloy-4)under free potential and controlled potentials.In this case the anodic area(Fresh Surface Area)is equivalent to the wear scar area.Chemical factor is not severe for wear of pure aluminum and zircaloy-4.，where the mechanical wear，obtained at cathodic potential in the polarization curve from PP method，governed the wear。However，the steep potential drop occurs with the start of sliding and saturated soon.In this research the anodic area was assumed as the projected wear scar area，the real wear scar area considered the surface roughness，Hertzian contact area。If corrosion current density at the fresh surface is obtained from the PP method，the contact area during sliding would be estimated.This has not been cleared yet.Qualitative property of dynamic corrosion，therefore，is cleared in this research，even though the quantitative property is not sufficient。

We have investigated the corrosion behavior under sliding condition. Such condition is referred as dynamic corrosion, because on the surface suffered sliding friction fresh surface is exposed continuously and the corrosion behavior is quite different from ordinal corrosion, I.e., static corrosion.The electrochemical approach is very effective to understand the corrosive or electrochemical factor contributing corrosive wear. However, corrosive factor is determined by the product of area of the fresh surface exposed and corrosion current density of the fresh surface. Unfortunately both parameters are unknown. We assumed that the corrosion current density was estimated from the current density obtained by potential pulse method (PP method) .Wear experiment was carried out in NaィイD22ィエD2SOィイD24ィエD2 solution for SUS304 stainless steel, pure iron, pure copper, 6-4 Brass, pure aluminum and zirconium alloy (zircaloy-4) under free potential and controlled potentials.This evaluation method was quite good for corrosive wear of SUS304 under reciprocating sliding, continuous sliding and scratch test. In this case the anodic area (fresh surface area) is equivalent to the wear scar area.Chemical factor is not severe for wear of pure aluminum and zircaloy-4., where the mechanical wear, obtained at cathodic potential in the polarization curve from PP method, governed the wear. However, the steep potential drop occurs with the start of sliding and saturated soon.In this research the anodic area was assumed as the projected wear scar area, the real wear scar area considered the surface roughness, Hertzian contact area. If corrosion current density at the fresh surface is obtained from the PP method, the contact area during sliding would be estimated. This has not been cleared yet.Qualitative property of dynamic corrosion, therefore, is cleared in this research, even though the quantitative property is not sufficient.