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Problem Description Probable Remedies
Powdery, dusty coating
  1. Phosphate bath temperature too high.
  2. Excess sludge in phosphate bath.
  3. Process time too high.
  4. High Fe content in pickling bath & low acid concentration.
  5. Abnormal high accelerator concentration.
  1. Lower down temperature.
  2. Bath desludge.
  3. Maintain process time.
  4. Discard the pickling bath/correct acid bath conc.
  5. Reduce accelerator as desired.
Hard, coarse coating
  1. Insufficient acceleration.
  2. Iron build up in phosphate bath.
  3. Poor cleaning.
  4. Lack of inhibitor in pickling acid.
  1. Correct accelerator level.
  2. Convert phosphate bath to nitrite side.
  3. Improve cleaning process.
  4. Proper inhibitor to be used.
Loose coating
  1. Phosphate bath acid ratio is too high.
  2. Cleaning is not proper.
  3. Fe content in pickling bath too high.
  1. Correct acid ratio.
  2. Improve cleaning process or install jet pressure spray.
  3. Discard the pickling bath.
Light phosphate coating
  1. Degreasing is poor.
  2. Accelerator is too high.
  3. Acid ration of phosphate bath too low.
  4. An oxide on metal surface formed in stroage.
  1. Improving degreasing.
  2. Maintain accelerator to desired level.
  3. Correct acid ratio, check acid carry over.
Rough blotchy and non uniform phosphate coating
  1. Flash drying in drain stage prior to phosphate.
  2. Over Pickling.
  3. Poor descaling.
  1. Reduce drain time.
  2. Avoid over pickling.
  3. Improves descaling.
Incomplete coating
  1. Poor cleaning and/or rinsing.
  2. Short treatment time.
  3. Insufficient accelerator.
  4. Metallurgical condition: heat scales metal oxide, poor steel quality.
  5. Excessive sludge formation in phosphate bath.
  6. Phosphate bath parameter our of range.
  1. Check cleaning.
  2. Maintain processing time.
  3. Correct accelerator.
  4. Remove with organic acid.
  5. Desludge the bath.
  6. Correct phosphate bath parameter.
Poor corrosion resistance phosphate coating
  1. High Chloride ion build up in phosphate bath.
  2. Salty water used in process.
  3. Poor rinsing after acid pickling.
  4. Storage in corrosive area.
  1. Discard the bath & prepare fresh bath.
  2. Soft water to be used.
  3. Improve acid rinse.
  4. Keep away phosphate treated material form corrosive or humid area.
 

 

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