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Cold sealing bath contamination

2007

Does anybody know which contaminant and the maximum concentration of them that can't make a nickel fluoride sealing bath stop sealing or do not reach the minimum sealing quality?.

Right now I'm checking the sulphate (1600 ppm) and phosphate concentration (25 ppm)and I'm not sealing properly (2 colorant stain test).

Best regards,

Sergi Fernández
Anodizing shop employee - Spain

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2007

Hi Sergi Fernández,

Before mentioning about impurities, the Ni:F( 2:1)ratio is mainly to be monitored. pH of range about 5.5 to 6.5 (please follow the Supplier's recommendation. These two parameters are critical.

Impurities:

Iron contamination is a possible impurity, if your tank is of steel or any steel work in your tank, comes in contact with the liquid.(I faced this problem because of using SS 304 - tank without passivating, this you can make out : i.e you can observe light yellow colored layer after sealing )

Aluminum can contaminate as a reaction impurity

Calcium, potassium, Sodium, chlorides etc may be from the water either in the bath or by carry over from the pervious tanks.

Other than these,
After Cold Sealing, a post treatment of hot water(de-ionized)rinsing (like about 8-10 min for 10 micron thick of anodic layer at around 60- 65 deg C) will give better corrosion resistance.

don't test the components immediately after it comes out of line (leave it for aging) normally the aging time for cold impregnated components is about 24 hours(as per literatures). I take it after 4-5 hours of aging for tests.

Hope this helps...good luck.

Keshava Prasad M
- Chennai , India