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If the zinc coating is good, but when the light comes out in 3% nitric acid, there is a dark shadow on the coating, and the film is brown when passivation occurs, which may be caused by foreign metal impurities such as copper or lead in the galvanized liquid. When there is a problem in the process of galvanizing, check the temperature and current density first, and then measure and adjust the content of zinc and sodium hydroxide in the bath through the analysis of the bath. Whether DPE levels are low can be determined by Hull cell test.

Cold galvanized, generally speaking, do not need heating, galvanized amount is little, this galvanized parts are easy to fall off in wet environment. Hot dip galvanizing, also known as hot dip galvanizing, is to melt the zinc ingot at high temperature, put some auxiliary materials in, and then dip the metal structural parts into the galvanized groove, so that the metal members are attached to a layer of zinc layer. The advantage of hot dip galvanized is that its anticorrosion ability is strong, the adhesion and hardness of galvanized layer is better.