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Air pocket formation in boxes while dipping in phosphating bath

2004

We are using di-cationic dip phosphating system. Our components are of box type. We can load boxes(in the loading basket) only in vertical position and in such cases when we dip the basket in phosphating tank, a big air pocket forms at the inner top side of the box which restricts phosphating at that particular area and so this portion gets rusted. I can't load boxes in horizontal position because in this case the carry over of chemicals will be too high.(Boxes have no holes.)

I know air pocket is a disadvantage in any kind of dip process.

I want to know is there any solution to this problem ?

Manish Dhyani
UL - New Delhi, India

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The solution is obvious in principle but may be difficult and expensive to implement. The boxes should be racked approximately vertically in the baskets, but tilted enough to let the air out of that corner. During withdrawal the basket should be tilted to allow drainage. This approach has been used on programmed cranes for decades.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

Thank you very much for your solution to this problem.I am doing this practice but still I am facing the same air pocket problem. Geometry of our boxes is so complex.IS there any other method to solve this problem. Though I am going to implement some auto up down oscillation system of basket while dipping in the tank which will keep on displacing the air pocket and will reduce the bubble size. I have tried it manually and results are quite satisfactory but I am looking for some solid solution to this problem.If anyone can help.

Manish Dhyani
UL - New Delhi
2005