Stainless steel spray coating

Question

Stainless steel spray coating

nnosnhoj (Industrial)

(OP)

29 Jun 17 05:57

I'm using spray gun with automatic reciprocator system to coloring stainless steel sheet with some translucent lacquer. However, I found the color is unevenly sprayed and can't figure why is it uneven.
I've tried several ways including:
1.Different distance between spray gun and the steel sheet.
2.Different angle of the spray gun.
3.Moving speed of the spray gun.
4.Spray times and spray volume.
5.Air pressure of the spray gun.
6.Pressure of the lacquer.
7.Different temp and humidity.(64F~85F, 3X%~7X%)
8.Different spray gun.(Iwata LPA-200 and other locally manufactured spray gun.)

It looks like blushing but I think it's not blushing because the following reason:
1. Situation gets better when I tune the air pressure higher while it is believed to be worse if it's blushing.
2.I also tried different temp and humidity.(64F~85F, 3X%~7X%)
3.I've tried to heat up the steel sheet to about 85F-90F before spray but still in vain.

https://www.dropbox.com/s/ywldutnux2ajo9y/CBYK6496...
https://www.dropbox.com/s/ag5e6bqa4e0dfvf/DYHP5354...
https://www.dropbox.com/s/wnjfuga832mt4yb/EQMN2832...
https://www.dropbox.com/s/nyv5xg0c918n719/WAHC0552...

Is there anybody know the reason?

MikeHalloran (Mechanical) · Answer 1 · 2017-07-03 22:36:09

One time I applied too many coats of semigloss varnish to a wood surface, and got an irregular, blotchy, blushed result.
Semigloss contains 'flattening agents', which are fine particles of ... something, that can adhere to one another and form a semi-continuous sheet of whitish stuff.
Gloss varnish contains no such goo.

What, exactly, are you spraying?

No expertise claimed here.

Mike Halloran
Pembroke Pines, FL, USA

nnosnhoj (Industrial) · Answer 2 · 2017-07-04 00:47:30

Thank you for reply, MikeHalloran.
The translucent lacquer I'm spraying contains no 'flattening agents'.
What's more, the problem exists no matter I apply few or more lacquer on it.
Finally, I don't know the ingredient of the lacquer and I'm actually a greenhorn of spray tech.

Thank you very much again.

dik (Structural) · Answer 3 · 2017-07-04 01:01:59

RE: Stainless steel spray coating

dik (Structural) 4 Jul 17 01:01

What coating are you using?

Dik

Compositepro (Chemical) · Answer 4 · 2017-07-04 02:46:48

What surface prep have you done to the SS sheet? It seems your coating is not leveling well so it could be a surface tension problem.

nnosnhoj (Industrial) · Answer 5 · 2017-07-04 02:59:41

Thank you all,
I am using a translucent lacquer while adding some color masterBatch.

Compositepro, I've clean the SS sheet with acetone before spraying. I was wondering if it's not leveling well,too. However, the sheet looks leveling well IMO.
I just remind a important point: The situation gets better when I use hand gun instead of automatic reciprocator system.

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Stainless steel spray coating