Weldable Epoxy Powder-Coated Steel Tube

Date 06-01-2009 16:33

I would be very interested in your results if you will share them.
The concept is a great idea - if it works.

It sounds too good to be true. Powder coat epoxy is still epoxy and is made up of some nasty chemicals. The VOCs would likely be low because powder coating application is low VOC anyway - but that's paint application and not welding. It's what ends up in the welding smoke that I'd be worried about.

The claim seems to be that the very thin application, resulting in less paint to burn up, is the reason for success. From a painting point of view how many coatings are compatible with that primer? Will thin primer coat affect adhesion of subsequent coats?

Hopefully, the claims are proven true

By jrw159

Date 06-01-2009 16:46

Chet,
I will for sure share the results. :-)

See page three of the link, "• EPOX Z KOTE Tubing is free from all solvents and does not emit any Volatile Organic Compounds (VOC’s)during application and welding." It appears they claim this for the welding as well. I too am worried about the fumes.

After I do the weldability test, we are going to powder coat over the top of this primer to find out how that works for us with adhesion. We primarily powder coat everything, and very little of our stuff gets paint so I am not sure if I will be able to get any info from that side. However, I think that if the powder coat process adheres well, most likely paint would too, but I am NOT a paint guy, so that is just me talking. Any thoughts?

And again, I will share pic's and results as soon as possible.

jrw159

By welderbrent (*****)

Date 06-01-2009 23:13

John, as we use a lot of powder coated products, I am very interested in your findings as well. Had not heard of this from my suppliers. Intend to ask some questions. Thanks for the techno update.

Have a Great Day, Brent

By CHGuilford (****)

Date 06-02-2009 13:43

My thoughts are that there are coatings that should adhere with no difficulty but not many paint manufacturers will warranty their products if they are applied over someone else's paint. That does not automatically mean a problem, just that the homework needs to be done.

As far as VOC's, that is normally the stuff in paint that evaporates during curing. It seems a safe bet to state low VOC's during welding because there shouldn't be much anyway. So that looks like a marketing topic aimed at keeping environmental agencies happy. Again, not an issue, it's just a statement.

The real concern I think is that welding over any coating generates fumes that should not be inhaled. That goes for any welding, but I would be concerned that the low VOC statement might lull some folks to think there is no problem. In reality, it's not the VOC level we need to worry about. Good ventilation is needed, but that goes for any welding.

The fact that the paint is 1/2 mil thick means there should not ba a lot of paint to burn off in the arc - not a guarantee that there will not be porosity but will probably work out OK.

As I said, it sounds like a good product, but the buyer should do the homework to avoid problems.

By jrw159

Date 06-02-2009 15:15

Yeah, PEL's are what need to be looked at. I received the welding fume test results today. I have not had a chance to look through them completly, but what I have looked at shows below OSHA's PEL's. Here is the front page. The other file is too large to attach so if anyone is interested, PM me an e-mail address and I will forward it on.

jrw159

Attachment: 080054AtlasTubeWeldingFumeTestEpoxZKoteResults.pdf (77k)

By eekpod

Date 06-03-2009 10:27

Look at the last page, second from the bottom paragraphof the WPS. Where is says AWS does not require the coating to be removed, and that it should be qualifed per section 4 of the code.

It looks like they are coming from the angle of "produce objectional fumes". I guess if they consider this coating a "thin rust inhibitive coating" you may be ok, still it might be a goog idea to run a PQR per section 4 to cover yourself just in case. If a weld ever failed, a good lawyer may try to go after you, you never know these days.

Powder coating is basicallt the pigment without the thinner, thats why its applied dry and it takes an oven to bake/ cure it versus the thinner to evaporate out of wet paint.

By jrw159

Date 06-03-2009 11:39 Edited 06-03-2009 11:41

That is correct. They recommend for critical structures, which ours are, qualification testing with clause 4 of D1.1 and this is basicaly there to cover them. I will most likely end up qualifiying a procedure regardless of how well it welds for the reasons you hyave touched on.

I have contacted AWS and they consider it a "thin rust inhibitive coating" so it's removal is not required.

As for objectional fumes, the weld fume analysis shows levels equal to welding uncoated steel. As stated earlier, if you would like the break down, PM me your e-mail address and I will forward it as it is too large to attach. Part of it is 12 pages and the other is 28 pages.

jrw159

By eekpod

Date 06-03-2009 12:11

I'm curious to see how the test results go for the PQR. I think your on the right track, run it to confirm it works and gives you the weld metal characteristics and you should be fine. Keep us posted, good luck.

By Joseph P. Kane (****)

Date 06-03-2009 19:25

John

Please tell me WHO in AWS said it is a "thin rust inhibitive coating" so it's removal is not required. " ???

I am unaware of any AWS Official interpretation on this product or any other product.

I can remember hearing this about the "Bloxide" aluminum coating twenty years ago, and it allegedly did not enter the weld atmosphere or weld melt, because it supposedly evaporated from the heat of the arc long before the molten base metal got near the coating. However, once again, there was no peer reviewed article and / or Committee consensus vote on the subject.

As it was described to me back then, it is OK if the proponent of the product claims that it is a "thin rust inhibitive coating" , and it is then up to the inspector or the owner to counter argue if they do not agree.

The code may say that "A thin rust inhibitive coating" may remain...", ETC. but that does not list individual products.

Joe Kane

By Lawrence (*****)

Date 06-03-2009 19:49

Been watching this thread with interest and a good amount of confusion.

I never understood this.. Maybe this is hijacking a thread.. Maybe it fits..

Every top flight poster here would say that it takes a PQR and some very specific controls in place to weld over Galvanized or painted metals... But what exactly are those if they are not a thin rust inhibitive coating.????????

Paint, Zinc, WD-40.. all thin rust inhibitive coatings.

How thin is thin?

Lots of things inhibit corrosion, many of them are based on hydrocarbons or other enemies of steel.

Don't like to be a synic but weasel words like "thin rust inhibitive coating" leave way to much to the imagination.

Well we diddn't mean paint or galvanized when we said "thin rust inhibitive coatings"....... Ok than what exactly is ment??????

By jrw159

Date 06-03-2009 19:56 Edited 06-03-2009 20:15

Lawrence,
I believe it fits perfectly and is, IMHO, not a hijack. I am sure most here know how I feel about welding through "coatings" and I truly see your point.

jrw159

By CHGuilford (****)

Date 06-03-2009 21:42

Lawrence,
My take is - if you weld it and don't get defects, then it's a "thin, rust inhibitive coating". If you get defects, then it's paint and you should'a ground it off first.

I know - big help I am.

By DaveBoyer (*****)

Date 06-04-2009 03:55

If You develope a procedure, follow it, test the parts and they make all the mechanicals, what would it matter if the material had been coated with peanut butter? [to be sarcastic] I understand Your point and agree.

By jrw159

Date 06-03-2009 19:50

Joe,
PM sent.

jrw159

By jrw159

Date 06-09-2009 12:26

Joe,
I called AWS and asked to speak to someone specializing in coatings. I spoke extensively with this person and then I sent him all the info I had on this product and requested that he e-mail me back after reviewing the documents. Here is the response I received.

"To document our earlier conversation, D1.1 does not forbid welding over products such as this, and specifically recognizes "a thin rust-inhibitive coating" (see D1.1/D1.1M:2008, 5.15).

You may use a prequalified WPS such as the one you forwarded below, although I too would recommend qualification testing to minimize the risk of rework. You may ask Atlas for their recommendations regarding consumable *brand names*, and you may also wish to do some welder training. Note that the current for the 0.045 wire should read 230 to 280.

As I mentioned, I am currently working on a new publication ... AWS D3.9 "Specification for Classification of Weld-Through Paint Primers" which should be published by the end of the year.

If you go ahead with the epoxy powder coating, I would be interesting in hear your results."

You are correct that AWS does not list by product, just description.

jrw159

By jrw159

Date 06-09-2009 12:40 Edited 06-09-2009 14:42

OK, so the test pieces have been welded and powder coated. We had no trouble initiating an arc with the plasma torch. We also had no trouble initiating the welding arc. The welds laid in nicely and showed no rejectable indications per AWS D1.1 table 6.1 and weld spatter did not stick to the coated surface of the HSS. We welded on some flat circle plates to see how closing the weld in would react. No adverse effects. This was done under the parameters set out by the manufacturer. At the powder coating stage we ran one set through untouched (we just wanted to see the effects) and when completed you could barely see the HAZ where the primer had scorched so the second set we wire brushed the weld area and then powder coated and the final product was good. I ran a very basic "chip test" and it appears that the powder coating adheres slightly better to the coated HSS than to the uncoated HSS, but not to a large degree. All in all the product appears to perform as advertised.

As for the welding fumes, the clear coat seemed to put of less fumes, but overall none of the fumes ex[elled by the welding process gave me any reason to doubt the test results provided.

Now there is a prequalified procedure that one could use with this, but as suggested (not required) I believe it best to go ahead and qualify a procedure if we do go forward with the use of this product. The use of this product is not my decision to make at this point in time. Purchasing will have to make that call depending on what kind of pricing they can get.

Now lets see if I can get the pics to attach. :-)

jrw159

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By eekpod

Date 06-09-2009 14:40

I'd have to say that it looks like your all set. I can't see any issues with the quality or appearance of those welds.
I'm glad you posted those, because out of habit, I would have had my guys remove the "paint" on the red primer tubes, that's just what I am used to seeing. But again, if you qualify the procedure to cover yourself just in case, even though its not required, I think your all set.
Good Luck
Chris