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Trouble Shooting Alkaline Zinc

Dullness in LCD Areas
Dullness / Streaking in MCD Areas
Pitting or Burning
Poor Thickness Distribution
Poor Plating Efficiency
Poor Adhesion / Blistering

Lack of Brightness

This problem is most usually caused by low brightener levels in the bath or low zinc levels. Analyse the bath for zinc metal content. If the zinc content is lower than the recommended value, correct this before making additions of brightener. If the zinc content is correct, the bath requires an additon of brightener. Perform a Hull Cell test and check the metal deposit thickness on the panel. Make a brightener addition, retest and recheck the thicknesses. If the plating efficiency of the bath is still OK (check with the data sheet for the relevant process), proceed with the brightener addition.

Dullness in LCD Areas

This problem is due to a high zinc concentration in the bath, low sodium hydroxide concentration or lack of brightener (or carrier in the case of Envirozin 100, 120 or Genesis). The method of correction for this fault is as follows:

1.        Analyse and, if necessary, correct the sodium hydroxide and zinc concentration in the bath. It is important that no additions are made to correct faults until the basic bath composition is correct.

2.        After correction of the basic parameters, perform a Hull Cell test. If the LCD problem is still apparent, an addition of brightener is required in the case of Envirozin 5 or 6. Follow the data sheet for these additions. In the case of Envirozin 120 or Genesis, lack of Carrier can also produce this defect. The first thing to do in the case of these processes is to add 1 ml/l of Base Additive (Envirozin 120) or Carrier (Genesis) and repeat the Hull Cell test. Measure the thicknesses on both the original panel and the panel with the Carrier added. If the difference is more than 20%, do not add carrier. If the LCD problem persists, do not add Carrier or Base Additive to the process tank. In these cases, brightener rather than Base Additive or Carrier is required.

Dullness / Streaking in MCD Areas

This problem is caused by a lack of Conditioner (Envirozin 5, 6, 100,120) or Replenisher (Genesis). The concentration of these components can be analysed in our Technical Centre and we would recommend that this analysis is carried out at least once every month. Follow the data sheet recommendations for each process but bear in mind that in hard water areas, or when carbonate levels in the bath are high (Envirozin 5, 6), a higher concentration of Conditioner or Replenisher may be required.

 

Pitting or Burning

This problem is caused either by excessive zinc concentration or lack of Carrier in the bath. Again, the bath should be analysed for zinc concentration before any addition is made. If the zinc concentration is correct, the bath requires a Carrier addition. In the case of Envirozin 5, 6 and 100 the carrier components are incorporated in the brightener as a "one shot" additive. In the case of Envirozin 120 and Genesis, it is added as a separate additive. The concentration of this component in both of these processes is critical to bath performance (efficiency and deposit thickness distribution) so be sure to follow the data sheets carefully.

If an addition of Base Additive (Envirozin 120) or Carrier (Genesis) increases the amount of burning on the panel, this indicates excessive chloride contamination of the bath. Chloride is a serious contaminant which can lead to an intolerance of Carrier. Eventually, this will lead to problems of blistering and poor throwing power. If excessive chloride is suspected, send a sample of the plating bath to our Technical Centre for diagnostic analysis.

Poor Thickness Distribution

This problem may be caused by excessive zinc concentration or lack of sodium hydroxide in the bath. Again, before any additions are made, the bath should be analysed for zinc and sodium hydroxide and corrected. If the basic composition of the bath is correct, then the bath is low in Carrier (Genesis) or Base Additive (Envirozin 120). Follow the data sheet for the correct additions for each process.

 

 Poor Plating Efficiency

This problem may have several causes. These are as follows:

  • Low Bath Temperature
  • Very High Carbonate (above 80 g/l)
  • Low Zinc Concentration
  • High Additive Concentration
  • Bath Contamination

The temperature and zinc concentration can easily be checked and corrected. High carbonate can be a problem in solutions with low dragout. It can be removed by "freezing out", either using special equipment or pumping out the bath after winter shutdown.

High additive concentration can be a potential problem. It can happen if additions are not properly monitored or if dosing pumps become faulty. Carrier or Base additive can build up in baths and can take a very long time to plate out. Bath contamination is quite common. Pretreatment is rarely perfect on commercial zinc plating lines and oil or other contaminants can be dragged into the bath.

If the carbonate is low, the zinc concentration correct, the bath temperature OK and plating efficiency still poor, send a sample of the process solution to our Technical Centre for diagnostic analysis.

Poor Adhesion / Blistering

This can be caused by several factors:

  • Poor Pretreatment
  • High Zinc Concentration
  • High Additive Concentration
  • Low Bath Temperature
  • Bath Contamination
  • Lack of Carrier

By far the most common cause of poor adhesion and blistering of the deposit is poor pretreatment. This should be investigated thoroughly before suspecting any other cause. Please refer to our section on preferred pretreatment systems for our recommendations.

If you have checked the bath temperature, pretreatment, zinc concentration and additive dosing rates and this problem persists, send a sample of the process solution to our Technical Centre for diagnostic analysis.