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E-coat over welds

I am setting up an e-coat line in Alabama. The primary part is a winch that has a sprocket welded to a center spool. My question is in regard to voids in the finish around the area of the welds. What is the best way to resolve this issue ? Additions to the pretreatment chemicals or changes in coating type ?

Bob Hamell
product designer - Prattville, Alabama
August 3, 2009

Painting over weld areas can be problematic since there can be a lot of "junk" there, including carbon residue that's hard to remove. I've seen acid pickling sometimes help with this. You should probably concentrate on the cleaning step of your pretreatment line and see if changes there can help.

Christian Restifo
- Pittsburgh, Pennsylvania
August 13, 2009

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The only sure cure for this is mechanical, the welders or metal finishers(if you have a finishing step)should prep this area for paint while it is still in their hands as it is flux and other welding contaminates that will cause the problem.

I know the exact thought that went through your head as you read this as I have been a painter for 20 years and have suggested it many times in places that I have worked :-)

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
August 15, 2009

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Hello,

I've seen the Acid pickling step worsen the bleed out rust, but I guess it would depend from weld to weld.

Personally I would touch up the entire weld and unwelded area with a stroke of touch-up paint or zinc plate the part before Assembly and CED coating.

Unfortunately there is no other way to overcome this.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

September 28, 2009