Low pH Activation Bath: Smart Fixes for a Serious Problem

Summary for low ph activation bath Discussion

Very low pH in activation bath is the core issue in this tri-cationic phosphating thread. Babu Sankar said the surface activation bath total alkalinity was drifting low, at 1.2-1.5 instead of the 1.8-2.2 spec, and asked why. David Hall advised that the bath should be controlled by total titanium, filterable titanium, and pH, not alkalinity alone. He said a falling pH/alkalinity can come from contaminated or unsuitable replenishment water, suggesting de-mineralised water if town water is suspect. He also warned that phosphate solution may be spraying back from misdirected entry sprays or along the conveyor shroud, which can lower pH and worsen the problem. Hall further recommended asking the chemical supplier to investigate whether the product is wrong for the operating conditions. Later, Nikhil reported the same issue even with good DI water and no obvious contamination, and Ted Mooney asked for the titanium and pH readings and whether the supplier had been pressed to investigate.