Abstract
In previous work, crevice corrosion of pure chromium was modeled by coupling polarization curves with the water-hydrogen-chromium-chloride heterogeneous phase diagram. Assuming equilibrium conditions in the crevice, the time stepwise-calculated development of the critical crevice solution was quantitatively shown to initiate crevice corrosion through a breakdown of the passive layer, which was followed by the formation of chromium chloride and the subsequent acidification of the crevice solution. In the present paper, the same principles are applied to pure nickel with the main emphasis on the determination of the effects of bulk levels of pH, chlorides, and oxygen, at constant crevice geometry frequently applied in experimental work with a remote crevice assembly (RCA). As a result, increasing chloride contents, bulk oxygen levels, and decreasing pH reduce the calculated initiation times for passive layer nickel hydroxide (Ni[OH]2) breakdown, representing the crevice corrosion start as well as the times for total dissolution of the passive layer. At the same time the mean crevice corrosion currents are reduced by increasing chloride contents and pH as well as by decreasing bulk oxygen levels. Although these results are qualitatively in accordance with the behavior of chromium previously reported, the incubation times for nickel are shorter because of its specific properties at respective conditions. The goal of this paper is to convey a basic understanding of the crevice corrosion process with the participation of nickel in respective alloys.
