Tig Wire Coatings

Date 02-05-2011 10:25

There has been some debate concerning the copper coating on 70S-2 GTAW Wire. The argument is that the copper coating should be removed before welding. I understand that you would not remove the copper coating in GMAW, but the debate still comes up. There has been discussion that the copper coating is from the drawn wire process and is a by product of cheaper drawn wire process and is not a desired result in producing welding wire. It has been said that better quality wire does not have copper coatings in its drawn wire production process.

Others state that copper coating should be sanded or removed before welding much like you would clean the base metal before welding. Both propents and opposers say that the copper coating helps the metal from rusting which may be true. I have even heard that the coatings may have certain properties and chemicals which improve weldability or other properties and shouldn't be removed.

I understand it may just be a matter of prefrence, but I am looking for both PROS and CONS for removing this coating, weither wire with out the coating exist and if it is superior, and if there are any applications where the coating must or must not be removed (i.e. critical components).

By aevald

Date 02-05-2011 12:43 Edited 02-05-2011 12:52

Hello again diverdileo, I have included a link which may explain much of your questions about the "copper" coating that you speak of in your questions and statements. You will need to read various sections to understand how particular additives can affect weld metal deposits. Best regards, Allan

In particular check out page 22 of this PDF, it gives some very good descriptions of the different chemical additions from one S number to another

http://www.prest-o-sales.com/other_links/gases/PDF/ShieldingGases/Manuals/GMAW%20of%20Carbon%20Steel.pdf

By 803056

Date 02-05-2011 16:37

The copper flash is very thin and is generally vaporized by the welding arc.

Several years ago OSHA leaned on the filler metal manufacturers by taking the position that the copper was a heavy metal and needed to be controlled. The manufacturers stopped applying the copper flash to the iron based alloy filler metals. The filler metals would then form form a blush of rust if left exposed over night or after a short while even when the shop was relatively dry. The problem was so severe that the manufacturers started to apply the flash once again to quell the huge outcry from the welding industry.

The amount of copper reaching the weld pool in very low and does not affect the weld quality. Copper has limited solubiity in iron, so there is some tolerance for the minor amount that does reach the weld pool.

Best regards - Al

By Metarinka (****)

Date 02-13-2011 18:34

weld qualification is based on mechanical and destructive testing (among other things) if the weld can pass tensile and bend tests, it most likely will exceed service use conditions.

from my understanding most would flash off, prior to welding and I've never read it having an adverse affect on steel save for maybe impacting carbon equivalency. Then again the dilution even by volume would be very minute.

Other alloys and metals may have more of a problem with copper contamination, but usually only rust prone steel is coated.

By Lawrence (*****)

Date 02-05-2011 16:34

After reading Allan's excellent link, when it's time to decide.

Do not choose to try to remove the copper flash-coating.

Either select the copper coated filler wire, or find a vendor of uncoated wire.