hedger

Topic: Powder coating galvanized overhead hwy. sign structure

After we built a large sign structure for hwy use, the spec called for glavanizing and then powder coating. Which we outsourced now we are experiencing outgassing and pinholing. Is this from not properly prepping the surface or could the glavanazation process somehow leave residue or something that can outgas?

For future reference is there a recommended preocdure?

Any and all help would be appreciated.

Thank you

ChemSlinger

Re: Powder coating galvanized overhead hwy. sign structure

hedger,

The pinholing could likely be caused by a small amount of soil on the surface of the part, or either the paint was not cured enough.

The most common procedure out there is as follows:

Clean

Rinse

Prepare Surface (ie iron phosphate, zirconium coating, etc) 

Rinse

Seal (optional depending on the process)

Dry Off (you should see a nice "sheet" look as the part dries, no water beads)

Paint

Cure (Cure time and temp will depend on paint)

The steps above are the formula for a very clean, long lasting, powder coated part.

Hope this helps

EnviroServe Chemicals, Inc.

(910) 892-1791

ChemSlinger's Website

hedger

Re: Powder coating galvanized overhead hwy. sign structure

Thanks this is a big help

Travis Stirewalt

Re: Powder coating galvanized overhead hwy. sign structure

Hedger and ChemSlinger,

Good topic here. I have been involved with the same type process recently.

One thing we have noticed is that the quality of the galvanizing has a direct impact on the outgassing and powder coating success. Our recommended process would include ChemSlinger's recommended pretreatment process and then and outgassing stage in the oven. Heating up the past past cure temperature by 25+ deg for an extended amount of time can help. 

We would also recommend a powder coated primer as the first layer which is allowed to 1/2 cure in the oven and cool prior to the top coat of powder.

We have seen dramatic reduction in outgassing with these steps.

Have a great weekend! 

Travis Stirewalt, CSI, NASF
Senior Sales Manager, Eastern US
TIGER Drylac USA Powder Coatings
www.tiger-coatings.com

Travis Stirewalt's Website