Troubleshooting
Zinc Phosphating
Coating defects, de-greasing, rusting, streaking
Coating weight too low
CAUSE
SOLUTION
Phosphate or accelerator concentration too low
Increase concentration
Phosphate bath temperature too low
Increase phosphate bath temperature
Process time too slow
Lengthen time phosphating stage
Coating weight too high
CAUSE
SOLUTION
Phosphate or accelerator concentration too high
Decrease concentration
Process time too long
Shorten time
Powder on coating
CAUSE
SOLUTION
Poor rinses
Keep rinse overflowing
Excessive sludge
De-sludge tank
Accelerator concentration too high
Allow concentration to drop
Higher bath temperature
Lower the temperature of the bath
Spotty coating
CAUSE
SOLUTION
Poor cleaning
Check cleaning tank
Low concentration of phosphatizer or accelerator
Increase concentration
Poor solution coverage
Check racking and nozzles
Resistant to metal
Add Jernstedt salts to rinse or lean tank
Rusting
CAUSE
SOLUTION
Coating weight too low
See “Coating Weight too Low”
Final dry-off too slow
Increase temperature in the final rinse using air blow off
Dry-off between stages
Run at lower temperatures, better placement of nozzles
Higher free acid pointage in phosphating bath
Reduce the free acid pointage
Poor exposure to cleaner solution
Increase the pressure if necessary
Streaking
CAUSE
SOLUTION
Poor cleaning
Check cleaning stage
Poor rising
Better arrangement of nozzles
Dry-off between stages
Use fog nozzle, run at lower temperatures