Q：What are the common types of impurities?
A:Metal ion impurities, organic impurities, anion impurities, solid particle impurities.
Q:What effect do impurities have on coatings?
A:Metal ion impurities: the coating becomes black, flowery, the glossiness decreases, or even the coating is missed.
Organic impurities: the coating becomes more brittle, pinholes appear, and the brightness is uneven.
Anionic impurities: anode passivation, reduced current efficiency, and rough coating.
Solid particle impurities: particles on the surface of the coating are raised and the bonding force is poor.
Q:What are the methods for monitoring impurity content?
A:Chemical analysis and testing: metal ion detection, organic impurity detection, anion detection.
Electrochemical performance monitoring: Hull cell test, cathode polarization curve test, coating appearance and performance testing
Q:How to control impurities from the source?
A:Ensure that the pre-treatment is thorough (avoid residual grease and metal debris from the workpiece into the plating solution).
Use high-purity anodes (such as 99.99% zinc anodes) and deionized water to prepare the plating solution to reduce the introduction of impurities.
Regularly clean the residue at the bottom of the plating tank to avoid the accumulation of solid particles.
Q:What are the methods for removing impurities?
A:Metal ions: Add masking agents (such as adding tartaric acid to mask Fe³⁺ in acid zinc plating) or remove by electrolysis (low current density electrolysis).
Organic impurities: Regularly adsorb with activated carbon (1-3g/L), add additives after filtration.
Solid particles: Strengthen filtration (use a circulating filtration system with a filter element pore size ≤5μm), and open the filter for 2-4 hours every day.