Dear Joe,

We currently use a "Midnight Black” wrinkle powder coating supplied by a major powder producer. Can a second touchup coat be applied after first coat has cured? The first coat is being applied over cleaned HRPO (hot-rolled, pickled and oiled) steel. The second touchup coat does not adhere to the first coat and flakes off easily. Any comments, suggestions?

Regards,

Loyd Fields

Texas

Dear Loyd,

Recoating wrinkle finishes can be a headache. This product is epoxy based, which makes the task even more difficult as epoxies cure “hard” and are less receptive to recoating. Your best option is to scuff sand the entire surface to be recoated, blow it off, then solvent wipe with acetone or MEK. This may provide the adhesion you need.

Using a polyester-based wrinkle is another option. These are not as hard as the epoxy wrinkle, which should make recoating somewhat easier. However the polyester wrinkles are more sensitive to substrate surface defects and pretreatment streaking. HRPO steel can sometimes exhibit imperfections that will probably interfere with the development of a polyester wrinkle finish.

Therefore, I would first try the scuff sanding, followed by solvent wiping. If this doesn't work, you may be relegated to stripping the defective parts, cleaning them and powder coating a virgin surface.

Good luck with sorting this out. Let me know how things progress.

Best Regards,

Joe

Have a question for Joe Powder? Email kevinbiller@yahoo.com. And be sure to listen to the Ask Joe Powder “Powdcast” for all the latest news, insights and technology in the powder coatings industry. Click here to listen!

Dear Joe,

We currently use a "Midnight Black” wrinkle powder coating supplied by a major powder producer. Can a second touchup coat be applied after first coat has cured? The first coat is being applied over cleaned HRPO (hot-rolled, pickled and oiled) steel. The second touchup coat does not adhere to the first coat and flakes off easily. Any comments, suggestions?

Regards,

Loyd Fields

Texas

Dear Loyd,

Recoating wrinkle finishes can be a headache. This product is epoxy based, which makes the task even more difficult as epoxies cure “hard” and are less receptive to recoating. Your best option is to scuff sand the entire surface to be recoated, blow it off, then solvent wipe with acetone or MEK. This may provide the adhesion you need.

Using a polyester-based wrinkle is another option. These are not as hard as the epoxy wrinkle, which should make recoating somewhat easier. However the polyester wrinkles are more sensitive to substrate surface defects and pretreatment streaking. HRPO steel can sometimes exhibit imperfections that will probably interfere with the development of a polyester wrinkle finish.

Therefore, I would first try the scuff sanding, followed by solvent wiping. If this doesn't work, you may be relegated to stripping the defective parts, cleaning them and powder coating a virgin surface.

Good luck with sorting this out. Let me know how things progress.

Best Regards,

Joe

Have a question for Joe Powder? Email kevinbiller@yahoo.com. And be sure to listen to the Ask Joe Powder “Powdcast” for all the latest news, insights and technology in the powder coatings industry. Click here to listen!