Zn-Ca Phosphating Solution Improved by Baric Ion at Room Temperature

Several methods such as scanning electronic microscopy (SEM),energy dispersive X-ray spectroscopy (EDS) and sodium chloride solution corrosion testing were used to study how the Zn-Ca phosphating solution at room temperature was affected by Ba (NO3)2 and SO2-4.The results showed that SO2-4 could enter into the phosphating film and couldn’t be removed by water rinsing.SO2-4 could obviously affect the properties of the Zn-Ca phosphating solution and even lead it to be useless.However,when some Ba2+ (≤0.9 g/L) solution was added to the solution,the SO2-4 could be removed effectively.This can change the composition and increase corrosion resistance of the phosphating film formed from the solution.