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topic 45803

How to differentiate a powder coated finish from a sprayed finish?

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A discussion started in 2007 but continuing through 2018

2007

Q. Can you give me the methods to find out the powder coated finish as well as enamel (or epoxy) spray finish? And also give me the functional advantages of powder coating over enamel coating.

BOOPATHY PACKIRISAMY
QUALITY ENGINEER - PONDICHERRY, INDIA


2007

A. Hi Boopathy. If you can't tell, why does it matter? The principal driving force behind powder coating is its environmental friendliness because powder, unlike paint, needs no solvent and has no or almost no volatile content. If a component has an epoxy coating, I'm not sure that it's possible to say that the epoxy coating is in any way better or worse due to the fact that it was applied wet or as a powder.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


2007

Q. Dear Ted Mooney,
My customers are paying more for powder coating then spray painting and I am in a position to justify the rate difference.

As well as I have to prove to my customer that the finish is powder coating to convince him.

Please help me in this issue. I really need a systematic procedure to differentiate powder coating finish over spray finish and also technical advantages of powder coating.

BOOPATHY PACKIRISAMY [returning]
- PONDICHERRY, INDIA


2007

A. This is an interesting situation, Boopathy -- thanks for sharing it with us. But here is how you seem to have structured the proposition for your customer:

1. I claim that powder coating is a superior finish
2. I claim that my parts are powder coated
3. Here are the tests that I propose to prove my parts are powder coated.

Can I propose to you that the following approach may be better? --

1. I claim that the finish on my parts is better
2. Here are the tests that I propose will prove it.

Those tests might include abrasion, gloss (if it's a gloss finish), dielectric resistance (if that is important), dry film thickness, pencil hardness, etc. But first and foremost, a salt spray test on scribed panels.

Other readers are encouraged to participate; this is about as far as I can take the discussion. Good luck! Quality finishes cost more and quality finishes should pay more.

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E.
finishing.com
Pine Beach, New Jersey


2007

A. Here are a couple of ways that I can think of; powder has a higher first pass film build without the sagging/dripping of wet paint. P/C has better batch to batch consistency than liquid, you do not have to rely on operator error when mixing the reducers and catalyst. The powders used for industrial use is more resistant to deterioration/abrasion/weather than wet paint(salt spray a panel of each). Do the poor man environmental test on some sample panels, it's called the boil adhesion test. Cut a cross-hatch section in the painted surface and throw it in a pan of boiling water for 40 minutes, inspect the panel for paint deterioration and adhesion problems. There should be none. All of the environment concerns that Ted mentioned, not to mention that applying powder is significantly easier than applying wet paint. P/C is fully functional 30 minutes after it's applied. And why are you charging more for the P/C again?

Sheldon Taylor
Sheldon Taylor
   supply chain electronics
Wake Forest, North Carolina



2007

A. Hi Boopathy,

We need to compare the liquid and powder coating system with identical specifications. One such very important spec is satisfying salt spray resistance test.

A typical powder coated product with good phosphating should easily pass 1000 hours salt spray resistance with a DFT of 50 to 60 microns. This is a one coat system.

Whereas to have 1000 hours salt spray resistance in liquid coating with one coat and about 60 microns thickness is practically very difficult. A liquid system to meet 1000 hours will cost you multiple coatings (primer,mid coat & top coat).

Considering additional cost involved in paint, curing & labor a typical liquid system should cost more than powder system.

You may differentiate a powder coating with liquid coating by means of slight scratch of film.Try to scratch gently and look for a primer paint under a liquid top coat. Also the hardness and film thickness will give you an indication.Look for edge coating since powder coated products tends to have more thickness on edges compared to spray painted(dip painted will be different).

Thiagarajan.S
- Dubai, UAE


February 12, 2010

A. Dear Boopathy,
I agree with Ted Mooney and Thiagarajan, Powder Coating is a preferred process over Spray Painting where the application required better hardness and abrasion resistance (In simple words where physical movement/ handling of product is higher). This is purely customer perspective.
You might even get a Paint which can meet the hardness of powder coating, But I suppose the price might get higher than that of the Powder coating powder.

Sanjeev
- Hyderabad, AP, India



Very expensive powder coating didn't survive first B-B-Q

November 13, 2015

thumbsdownI purchased a brand new BBQ pit and paid an additional $800.00 for a powder coat finish. I got the BBQ pit on November 7 of 2015 so the pit is only 6 days old. I cooked on it one time and all the paint peeled off the lid to the fire box. It also started bubbling on the fire box and also came off to a bare grey metal.

45803

The place I bought the pit told me that was natural, the owner said for me to sand it down and re-paint it myself. Now I paid for a professional BBQ pit to be made to last. I should not have to re-sand and re-paint my BBQ pit after only one cook.

Richard Garcia
- Rockport, Texas, Aransas



Any Paint alternate to powder coating for Hospital beds?

September 18, 2018

Q. Hi,
I am a manufacturer of Hospital Beds. Most places Powder coating is used for coating in them, but the initial setup cost is coming out to be too high. This gave me a reason to explore if there is some other alternate. I have a paint shop, so if I get the right kind of paint to prevent rust, then I shall go for it immediately.

Need help in this.

Regards,

Rakesh Bhutani
Factory owner - India


September 2018

A. Hi Rakesh. Hospital beds are used indoors and probably in a controlled environment where corrosion resistance isn't even a major consideration anyway, and epoxy paints are probably fine.

But pretreatment remains important even for paint adhesion, let alone corrosion resistance. I'm not sure what systems you have when you say you have a paint shop. An auto painting shop can do acceptable wet paint on top of previous paint or on properly pretreated auto replacement parts -- but painting onto raw solvent wiped steel is probably not going to produce an acceptable finish. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
Striving to live "Aloha"



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