Passivation is to protect the material from getting rusty easily; which had been processed by zinc plating. After the parts have been dipped, they cannot be touched by hand. Before handling, the materials have to be heated by hot air. There are many factors which can cause corrosion. For example, condensed moisture of water drops, and the white rusty can be formed by itself. The process of passivation is to slow down and against the erosion of parts for making them look more shiner and longer lifetime used. The colours widely used are white, white blue, yellow, and black. The longest salt spray test hour is white, it can last for 280 hours.