2006 Volume 55 Issue 11 Pages 495-504
Crevice corrosion damages of a flat heald, 13Cr stainless steel components used for water jet room (WJL), was investigated in this paper. The healds had been operating in highly humid atmosphere of sprayed tap water, bearing heavy deposits composed of PAAE resin on their surface. Conventional group of heald (heald C) has used to serve for about two years, while a newly group of heald (heald X) suffered significant localized corrosion earlier in one or two months. Determined repassivation potential for crevice corrosion, ER,CREV, was expressed as
ER,CREV(mV vs. SHE)=-294 log[Cl-](mg/L)+832 (1)
in the Cl- concentration, [Cl-], from 20 to 1000 mg/L for metal/metal-crevice of the healds X and C at 30°C. ER,CREV for metal/deposit-crevice was confirmed at 16 mg/L Cl- to be close to the equation (1). Residual chlorine (R-Cl) concentration in the tap water increased as high as 0.4 mg/L, when spontaneous electrode potential, ESP, for the heald X might be believed to reach 570 mV vs. SHE (ESP,X). Based on comparison of ER,CREV as equation (1) with ESP,X crevice corrosion can be expected to occur above 8 mg/L Cl-. Conclusively, Cl- concentration of 14 mg/L in the tap water in summer could explain real crevice corrosion for the heald X. More ennoblement in ESP for the heald X than the heald C could be attributed to larger amount of precipitated Cr-carbide. To effectively prevent the crevice corrosion, R-Cl concentration in the tap water to be used for WJL should be kept below 0.04 mg/L.
