Abstract
The corrosion resistance of films deposited from electroless nickel plating baths was evaluated by outdoor-exposure tests, salt spray tests and an accelerated atmospheric corrosion (complex cycle) test under cycle conditions of 35°C in the test tank, 42min in 20-25ppm sulfurous acid gas ambient (<80% RH)→18min in 1% NaCl solution spray→102min in moisture (>85% RH)→78min in dry condition, for a total of 4 hours/cycle.Deposited films that contained above 10% P content obtained from pH4.3 malic acid baths were superior under both outdoor-exposure tests and the accelerated corrosion test. A correlation was recognized between air temperature, humidity, and wetness time as weather factors in the outdoor-exposure test on the one hand and corrosion loss on the other. Absolute humidity was found to have a cleared effect than relative humidity on corrosion resistance. Since the salt spray test for electroless nickel plating showed a poor correlation to the corrosion pattern in the atmosphere and required a long period for corrosion to begin, this method was not suitable for corrosion test of the deposited films. On the other hand, specimens corroded in 4 cycles of the accerelated atmospheric corrosion test were found to have surface appearance similar to that of specimens in the outdoor-exposure test and the pits produced were uniform in size and distribution over the surface.
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