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Troubleshooting guide for Zinc Phosphating

Coating Defects, De-Greasing, Rusting, Streaking

THERMASET POWDER COATINGS

UK's Largest privately owned Powder Coatings Manufacturer and Supplier

COATING WEIGHT TOO LOW

CAUSE

Phosphate or Accelerator concetration too low
Phosphate bath temperature too low
Process time too slow

REMEDY

Increase concentration
Increase phosphate bath temeperature
Lengthen time phosphating stage

Iron Phosphating

COATING WEIGHT TOO HIGH

CAUSE

Phosphate or Accelerator concentration too high
Process time too long

REMEDY

Decrease concentration
Shorten time

Metal Pre-Treatment

POWDER ON COATING

CAUSE

Poor rinses
Excessive sludge
Accelerator concentration too high
Higher bath temperature

REMEDY

Keep rinse overflowing
De-sludge tank
Allow concentration to drop
Lower the temperature of the bath

SPOTTY COATING

CAUSE

Poor cleaning
Low concentration of Phosphatizer or Accelerator
Poor solution coverage
Resistant to Metal

REMEDY

Check cleaning tank
Increase concentration
Check racking and nozzles
Add Jernstedt salts to rinse or lean tank

RUSTING

CAUSE

Coating weight too low
Final dry-off too slow
Dry-off between stages
Higher free acid pointage in phosphating bath

REMEDY

Increase temperature in the final rinse using air blow off
Run at lower temperatures, Better placement of nozzles
Reduce the free acid pointage

General Tips

Chromate Process

STREAKING

CAUSE

Poor cleaning
Poor rising
Dry-off between stages

REMEDY

Check cleaning stage
Better arrangement of nozzles
Use fog nozzle, Run at lower temperatures