52038

Powder coating thickness of 120 micrometers  

April 30, 2009

Dear reader,

Here at our industry we apply powder coating with corona charging, my main problem is that i need to obtain a paint layer thickness of 120 micrometers, wich makes us have to paint (achievng about 70 micrometers), cure the paint and then paint it again, to achieve the desired layer thickness.
Do you ave any ideas of how we could achieve a layer thickness of 120 micrometers with just one application?

Giulianno Sperotto
Methods and processes analyst - Fortaleza, Ceará, Brazil

Pre-heat the metal substrate (90-110C) prior to applying powder. Also try... just lowering the Kv.

Terry Hickling Martex Paints Ltd    Birmingham, UK

Already tried lowering the Kv but it did not reached 120 micrometers, so we still had to apply two layers of paint, however, I'll try preheating the metal substrate and post here if the combined solutions worked.
As you may have noted from my other thread, we are already in full usage of our ovens and running short on floor space so this cannot be considered a long, or even medium, term solution, we hope that by installing IR ovens we we'll be able to use one of the old convection ones for a pre-heating process, thanks for the help!

Giulianno Sperotto
- Fortaleza, Ceará, Brazil

Terry's right, preheating is definitely the way to go, I think the parts will need to be a little hotter 200 degrees though, but you'll have to experiment with that.

Sheldon Taylor    supply chain electronics Wake Forest, No. Carolina

Few points may be helpful to come out from your problem.
1. product should be preheated before powder coating.
2. ask your paint supplier to increase the size of powder particles.
3. discuss with him the application parameters for new powder before painting.

THANKS

SURYAPAL SINGH
- DELHI, INDIA

Well, the idea of increasing particle size was discarded because it can get "stuck" within the corona pistol, and even so, our supplier thinks it´s hard for us to reach 120 micrometers with one layer, yet the possibility of installing an IR oven will increase our capacity and give us room to preheat our substrate, and thus possibly eliminating the necessity of double layer painting.
Thanks for the help, Surya!
As for preheating up to 200 degrees it still occurs in the problem stated before, our greatest choke on production is convection ovens, so using these to increase temperature on the substrate up to 200 degrees (it would take about 10 min in our ovens if i´m not mistaken), for another of our products (with greater substrate mass) it took only 150 degrees, so i think 200 degrees is too much, and is currently out of question because of the oven choke (at least until we get IR ovens!).
Thanks for the help, Sheldon!

Giulianno Sperotto
- Fortaleza, Ceará, Brazil