Thermoplastic coating on steel cracks because of electric welding joints

We manufacture MS steel products like refrigerator shelves and coat it with thermoplastic powder. But after few weeks it starts cracking from the welded joints. We use MIG/electric welding in joints. I also attach some images so that you can get a clear picture of my query.

Kindly check it and inform me as soon as you get some solution.

Thanks a lot

Hi, Tayyab.

You have not discussed your pretreatment system, but thermoplastic coating is not "shrink wrapping". You can't apply it to poorly prepared steel; as a minimum, you need to remove any slag and then phosphatize the components. Good luck.

Regards,

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

Dear Mr Mubasher,

Like it is already said, it is probably related to the pre-treatment of the surface before coating.
If I may ask, what kind of thermoplastic coating are you using?

Kind regards,

Meindert Crapts