The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Zinc rich primer under ripple finish powder coat

2002

I am designing a steel product for outdoor installation. I would like to use a zinc rich primer under a powder coat top coat. I also would like to use a ripple finish on the top coat to conceal the press in fasteners used. I tried to produce samples using a zinc rich powder coat available in Australia, but the ripple top coat flattened out to a smooth finish. I am told that this is due to using a green cure on the primer, and that there is no solution. My next alternative is to use a wet spray epoxy zinc rich primer. The substrate is electro-galvanized mild steel. Does anyone have any suggestions as to why the first combination failed, or whether there are any other alternatives.

Thanks,

Stuart Heldon
- Sydney, Australia

---

2002

Stuart,

If the only reason you would like a "ripple" finish on your workpieces is to hide blemishes, I would suggest using another texture. People around the world give different names to different finishes, but from what I understand a "ripple" finish does not have the best mechanical properties and I would not use it for an outdoor application. Try using a "fine" textured (sandpaper texture) powder. These powders are already used for outdoor applications such as satellite dishes and provide good outdoor durability (polyester) and hide blemishes effectively.

Failing this try Phosphating your work pieces instead of zinc primer.

Hope this helps,

Drew Devlin
- Lincolnshire

---

2002

I am very interested in finding out more about these sandpaper type finishes. Can you recommend a text or source of more detailed information? The powder sales rep did not mention this finish at all. Also, my product is highly susceptible to vandalism. Do you know how this finish compares in terms of ease of cleaning off spray paint and stickers?

Thanks,

Stuart Heldon
- Sydney, Australia

---

2002

Hi Stuart,

The texture in a "fine textured" powder is achieved by adding waxes, so the anti-graffiti properties should be higher than a standard powder. The top five powder coating suppliers all supply these textures.

Drew Devlin
- North Lincolnshire

---

2002

Hi Stuart, totally agree with Drew. I couldn't understand why the first option didn't work! I am a Senior Chemist in middle England, specialising on textures, etc.. I have before coated ripple finishes on a powder primer - with success. My reservations with a ripple finish would be consistency of texture, Drews suggestion of a Sandpaper type finish is spot on as they hide a multitude of sins, such as weldspot/blemishes, etc. In my opinion they are probably the easiest powder to use! & low reject rates.

Merry Xmas,

Steve Gill
- Staffs, UK