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Paint blistering problems with water based paint

July 30, 2008

I am currently painting hot rolled steel, rather large parts 30" x 75" in a dip tank process. I am washing parts then dipping them into water based paint and then baking them.

I am trying to get an idea on how much time I should allow for flash off, or drip off of paint prior to baking. Currently I am getting severe blistering. Our paint supplier has added de-blistering agents. I currently have 3 minutes of drip off time until part reaches oven.

Thanks

Greg Gaines
Manager - Zanesville, Ohio

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August 2, 2008

Dear Greg,
Your problem is the retention of moisture within the paint film causing blistering to occur in or near the oven at about 95-100 °C.
The drying problem is amplified by the moisture retained in the immediate air (due to evaporation of the water phase) that is surrounding the items whilst they are moving towards the baking oven. To overcome this you should try to remove and replace this heavily moistened air using a good air flow of fresh air (fans). A better option would be to utilise the warm air waste from your ovens to blow over the air-drying components (but not too hot). You may have to build a tunnel to concentrate these procedures.
Let me know if this helps

Terry Hickling
Birmingham, United Kingdom