There are solid particles in the plating solution. If the edge and tip of parts are rough, it may be that the current density is too large. If the galvanized layer is good, but in 3% nitric acid light, the coating has a dark shadow, passivation film appears brown, may be galvanized liquid copper or lead and other metal impurities. First check the temperature and current density, and then through the bath analysis, determine and adjust the content of zinc and sodium hydroxide in the bath, DPE content is low, can be understood through hull tank test.
If coating roughness is not the above reasons, it may be caused by the impurity in the plating solution, can take a small amount of plating solution, and filtering after the experiment, then take a small amount of plating solution, experimenting on zinc powder processed, check if failure is solid particles or copper, lead, and other different metal impurities, item by item, test, it is not hard to find the cause of failure. Incomplete oil removal or acid corrosion will cause large galvanized wire coating blister.
But the main reason for this kind of bath is easy to bubble is the adsorption of organic additives on the crystal surface of the coating, so that the original crystal or some crystal surface can not grow normally, resulting in the abnormal development of new crystal nuclei or some crystal surface; Or the organic additives in the coating clip, hinder the normal arrangement of the lattice, resulting in lattice distortion, thereby increasing the internal stress of the coating, resulting in coating bubbling.
Post time: 04-11-21