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Tapping issue with powder paint

Q. The company I work for produces cabinets and racks in steel.
We are gradually migrating from liquid paint to powder coating.
We are having right now some issues of excess paint in the holes which makes very hard the use of screws. We need to redo the threads which causes us considerable loss of time and money.
Have you ever met this problem with the powder coating? What are the parameters to be considered?

How could we fix it?

Thank you.

Nedjma Rahal
- Canada
January 10, 2012

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Its not easy to picture this from your description, but assume you have issues breaking the coating on re-tapping threaded or plain holes for fasteners in steel? cabinets.

Have you tried masking the holes? Good flexible silicone rubber plugs are available that you can press into the hole masking the thread, or inside diameter of a hole. Then no need to re-tap.

Geoff Crowley
Crithwood Ltd.
Westfield, Scotland, UK

First of two simultaneous responses -- January 12, 2012

The simple answer to your problem is to purchase a few dozen silicone plugs.These would be placed in the problem areas prior to PC and removed after baking. Can be used over & over again.

Terry Hickling
Birmingham, United Kingdom
Second of two simultaneous responses -- January 12, 2012

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The problem is more complex then that because of the type of product.
To give you a better idea, I would take as an example a mounting rail, which in our industry can have 130 threaded holes. So, the solution you suggested to mask them is not practical in our case especially since we can paint in batches of 50 or even more so ....
I'm wondering if there is any parameter or settings to play with to reduce the excess of powder in the holes.

Thank again for your help.

Nedjma Rahal
- Canada
January 13, 2012

Apart from increasing the Kv (trying to produce Faraday Cage??) which may then result in other defects (back ionisation)... then NO.

Terry Hickling
Birmingham, United Kingdom
January 16, 2012

Thanks to all of you for your comments and tips.

Nedjma Rahal
- Canada
January 23, 2012

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Just had one final thought,,, would it be worth considering that you powder coat first - then tap? The overall cost should be the same as tapping first.... but eliminating the extra labour cost of re-tapping powder filled holes?
I would be interested in any results you obtain.

Terry Hickling
Birmingham, United Kingdom
January 27, 2012

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If the color is black, try E-coating.

Ecoating does not exhibit charge concentration and the threads do not extra coating.

Also E-coat is typically 20 microns while powder coating is 50 to 80 microns.

Gurvin Singh
Mohali, Punjab, India
February 1, 2012