Why is the coating on galvanized products not completely degreased?
Reasons include: pretreatment solution temperature too low, insufficient ultrasonic power or electrolytic current, solution aging; excessive oil contamination on the workpiece, or oil contamination in the pretreatment and washing tanks. Solutions include: heating to the process temperature, adjusting ultrasonic and current parameters, regularly replacing the aged solution, manually pre-removing heavy oil contamination, and cleaning the tank.
What causes a dull galvanized coating?
Mainly due to: insufficient current, small and uneven anode area, insufficient brightener content; it could also be due to: excessively high zinc oxide concentration leading to an imbalance in the zinc-cyanide ratio, contamination on the substrate surface, poor conductivity, or intermittent current in the rectifier. Solutions include: adjusting the current and anode distribution, adding an appropriate amount of brightener, optimizing the plating solution composition, and inspecting the conductive system.
How to handle burn marks on workpieces after galvanizing?
This is often due to: excessive current, improper current distribution caused by an excessively small workpiece area, or excessively low zinc oxide concentration; it could also be due to: abnormal anode electrolysis, aging cathode electrolysis, or incomplete stripping. The following solutions should be implemented: reduce the current, properly match the components, replenish zinc oxide, replace the aged electrolyte, and thoroughly remove any substandard plating before re-plating.
What are the causes and solutions for hazy trivalent chromium passivation film?
Causes include excessively high pH value of the passivation solution, lack of air agitation or insufficient agitation, excessively long idle time after passivation, and excessively high zinc impurity concentration. The solution is to adjust the pH value and agitation intensity of the passivation solution, shorten the idle time, and replace the passivation solution if necessary.
Why does trivalent chromium passivation film develop mottled or black spots?
The core reason is an excessively low pH value of the passivation solution. Additionally, excessive impurities in the brightening solution and oil contamination on the surface of the components before passivation can also cause this phenomenon. The solution is to adjust the pH value of the passivation solution, replace the contaminated brightening solution, thoroughly remove oil contamination from the surface of the components, and then perform passivation again.