paint to cover stainless steel 3

[macPT]

Hi all!

We are about to start a project that includes outdoor AISI304 cabinets.

Our client want the cabinets painted.

Does anyone knows of any paint scheme adequate for stainless steel? Major issues: paint adehsion to the surface; corrosion resistance of coated stainless steel.

Regards

 

[Tofflemire]

Hi MacPT,

Powder coating works well, just make sure the that the cabinet surface is cleaned well prior to appling the powder coat IAW manufacturer's instructions.

FYI if you use powder coating, this baked on at 400 F, so if you have gaskets or other things that are temperature sensitive, then you may not want to pursue this.

Tofflemire

 

[macPT]

Tofflemire

Thank you for your input.

One thing that I have learned (can this be a tabu?) is that a stainless steel should not be isolated from the environment, so it can allways restore it's natural stainless coat. Can, the powder coating, prevent the stainless coat formation? Should this not be a problem?


Are you experienced in using this paint scheme on stainless steel?

Regards

 

[Tofflemire]

Hi macPT,

We have use SS enclosures to house electronic equipment in outdoor environments; they do oxidize with a brown film on the surfaces, so I can see why your client would want the finish covered.

As for the experience, we have just supplied powder coated SS items to be used in the open ocean, these items will be exposed to salt spray, so long term effects have not be seen.

I do have to agree with you concern, we had another project where SS hardware was used in deep water, the hardware disintegrated due to the lack of oxygen in the water.

You may want to post in the paint/coatings forum on this web site.

Tofflemire

 

[arto]

Don't forget to passivate -ref. ASTM A-967

 

[jay165]

The whole point of specifying stainless is to AVOID painting. I have never seen in my career an instance where SS was painted without the paint peeling off in large sections. Most memorable was at a DOE facility after the dimbulb ex-Army General manager insisted on it.

 

[Tofflemire]

Hi Jay165,

That's the best answer yet. My client was the Military who also requested these SS items be powder coated.

The only thing that I could add, the grade of SS specified was 304 which will still corrode.

Tofflemire

 

[macPT]

I also agree with jay165, but this is a non negociable subject to our client.

Tofflemire, you've said that you experienced problems in outdoor equipment. Have you done the SS passivation? We have experienced this kind of problems on non passivated SS components. But if you use your eqipment in very hard conditions (near the sea, for example) 304 is not the answer: you should use AISI316 (or 316L, if welded).

I've posted this subject in the paint/coatings forum as suggested.

Thank you for all your comments.

Regards

 

[arto]

The Dimbulb might not be so dim - Per the ASM Int'l-MEI CorrosionCourse book "If one of two dissimilar metals are to be coated, the more noble or corrosion-resistant metal should be coated."

It has to do with cathode to anode area ratios.
An example is given of steel-sided tanks with stainless bottoms. The steel was painted & developed many pin-hole leaks/perforations @ the paint defects. Once they painted the stainless too, the problem was under control.

 

[rlewis]

I work in the chemical industry, and we actually paint SS quite commonly to protect from chlorides. Abrasive blast is used to prepare the surface. The paint we most commonly use is an Epoxy primer and Epoxy finish. This works well. Although I can't supply you with our spec., paint manufacturers we use include Ameron, Carboline, ICI Paints, Jotun paints, PPG, Sherwin-Williams, Sigma, and Sika. Anyone of these paint manufacturers should be able to assist with the proper paint selection and application methods.

 

[jay165]

Hey "arto":

Re-read the original and my posts. What good does paint do when it is FLAKED OFF ON THE GROUND. Where does the orignal post mention galvanic corrosion?

 

[sbush]

Our experience is very similar to that described by rlewis above. We've been coating 304L pressure vessels with epoxy for over twenty years with no major problems. We use Tnemec, Sherwin-Williams and Ameron, high solids epoxys over a lightly-blasted surface prep. On leg or saddle base plate (bottom side) we use a heavy coat of bitumastic. These vessels typically see cold water on the inside and ambient air on the outside.

S. Bush

http://www.water-eg.com

 

[tickle]

I believe that grit blasting can help to provide a good protective coating on the stainless steel - it is too late on a friday afternoon to remember the details.

I have also painted St St heat exchangers that were found to corrode under insulation (chlorides and elevated temperatures in a warm environment). I think that a basic primer was used - it was a high temperature application so maybe not that basic - but it was something that I had used previously. I suggest approaching the painting contractors. In my experience they can provide the best knowledge - especially if they are going to warrant the painting.

 

[red300zx99x]

Powder coating should do the trick. Aslong as the surface is roughed(sand blasting proobably) and the complete surface is coated the coating should not come off. I would also assume that it should have little to no effect from the sea water, the coating basically puts a shell of plastic over the metal, good stuff.