THE ATMOSPHERIC CORROSION OF NICKEL IN A RURAL ATMOSPHERE

The initial corrosion behavior of nickel exposed under sheltered condi tions in a rural atmosphere has been investi gated using two starting dates in April and October. Emphasis has been placed upon short-term e xposure periods from 1 day to 4 months but longer exposure periods up to 1.5 years have also been included. A multianalytical approach has b een used to characterize the corrosion products, which have resulted i n a coherent picture with respect to both surface composition and morp hology Within hours of exposure, a thin film of NiO and Ni(OH)(2) is o bserved on the freshly polished nickel surface. After a few days, inde pendent of starting date, sulfate-containing corrosion products are fo rmed with characteristic dendritic morphology. The sulfate-containing corrosion products grow laterally and cover 25 to 30% of the nickel su rface after 120 days of exposure. Promoted by initial dry and wet peri ods and by increased concentrations of sulfate particulates, the forma tion of sulfate-containing corrosion products is faster in April than in October. After 1 year of exposure, the composition is NiSO4 . 6H(2) O.