There are many reasons why low chromium white passivation tends to appear color, and the common ones are related to the four aspects of the operation process.
(1) It is related to the imbalance of the process recipe in the passivation solution. The concentration of the white passivation solution is relatively low. When one of the components is consumed slightly faster, the proportion between the components will be out of balance, which will affect the quality of the film.
(2) It is related to the crystallization of the coating itself and the quality of the substrate. The coating itself is crystallized rough and base, the surface finish of the material is poor and the crystallized layer of the coating is fine, and the quality of the passivation film obtained from the workpiece with a good surface finish of the substrate is not the same. Practical experience tells us that the plating crystal is dense and the substrate surface is Workpieces with better finish are generally better after passivation, and are less prone to noticeable coloration. The passivation film layer, which has relatively coarse crystals and a poor finish on the surface of the substrate, is prone to iridescence, and the more crystallized the coating is, The worse the surface finish of the substrate is, the more severe the iridescence of the coating is (relative resistance).
(3) Relevant to the residence time in the air after passivation. The longer the air riddle before cleaning before passivation, the longer the color film is likely to appear.
(4) Incomplete cleaning. The passivation solution remaining on the surface of the workpiece will continue to react chemically with the zinc layer. At this time, the obtained passivation film is usually easier to be colored.In order to obtain a pure white passivation film layer with excellent quality, in addition to the above-mentioned several wine aspects in the operation, in the galvanization process, a plating crystal dense process recipe is used as far as possible, and the surface finish of the workpiece is also selected as much as possible. Good, non-corrosive spots.