Troubleshooting guide for zinc phosphatizing

Posted by: FEIHONG Powders |on July 3, 2018

Problem, Cause and Remedy

PROBLEM	CAUSE	REMEDY
Coating weight too low	Phosphate or accelerator concentration too low.	Increase concentration
	Temperature too low	Raise temperature
	Process time too low	Lengthen time
Coating weight too high	Phosphate or accelerator concentration too high	Decrease concentration
Coating weight too high	Process time too long	Shorten time
Powder on coating	Poor rinses.	Keep rinse overflowing
	Excessive sludge	De-sludge tank
	Accelerator concentration too high	Allow concentration to drop
Spotty coating	Poor cleaning	Check cleaning tank
	Low concentration of phospha-tizer or accelerator	Increase concentration
	Poor solution coverage	Check racking and nozzles
	Resistant metal	Add Jernstedt salts to rinse or to cleaner tank
Rusting	Coating weight too low	See “Problem-Coating weight too low.”
	Final dry-off too slow	Increase temperature in the fiial rinse-use air blow-off
	Dry-off between stages	Better placement of nozzles. Use fog nozzles. Run at lower temps.
Streaking	Poor cleaning	Check cleaning stage
	Poor rinsing	Keep rinses over-flowing
	Dry-off between stages	Better arrangement of nozzles. Use fog nozzles. Run at lower temps