Failure Reason of Corrosion Discoloration of Heat Sink Riveted Pin

Pins riveted with heat sink of a product had different degrees of discoloration and corrosion failure after high temperature and high humidity test. Macroscopic and microscopic observation with energy spectrum analysis were carried out on the corroded coating of pin, the cause of corrosion failure of the coating was analyzed. The results showed that the surface of pin coating was heavily corroded around the edges, the discoloration area of coating was mainly Fe oxide. Oxygen and water entered into coating via pores, cracks and other channels, and then oxidation corrosion of substrate Fe occurred, resulting in coating appearance bulging and cracking failure phenomena, etc. The C nonmetal inclusion in the coating facilitated the galvanic effect with metal element Fe and accelerated oxidation corrosion of Fe. In addition, differences in coating thickness led to different protection ability, so the product showed different degrees of corrosion. In order to prevent this kind of failure from happening again, the improvement process of the coating was proposed.