Welding through Paint and R/P
Welding through Paint and R/P
(OP)
I have been asked by the management at my site to consider a revision to the process of welding ASTM A27 grade 70-40 cast brackets to SAE 1022 housings with high Mn. The current process requires a fillet weld using ESAB Dualshield R-70 Ultra E70T-2 wire, 100% CO2 @ 35-40 cfh gas, which works very well for us. However the housings are now coming from overseas with paint or R/P applied in the joint areas to prevent rust. We are washing or grinding as appropriate to ready the surface for welding otherwise porosity will be present in the welds.
Now the management at my site informed me that our sister plant is welding through paint, etc., and that they have no porosity issues at all. Of course without any extra surface prep their productivity is better than ours so it's getting attention. They are using ESAB Dualshield T-63, 100% CO2 @ 60-75 cfh to weld the same materials.
I was always taught that you do not weld through paint and this just flies in my face. Even ESAB does not recommend any change, stating that I already have their superior product. I do not want to make this change and I have some support for my stand but I am very interested in my fellow metallurgists and engineers positions on the concept of welding through paint. Thanks!
Now the management at my site informed me that our sister plant is welding through paint, etc., and that they have no porosity issues at all. Of course without any extra surface prep their productivity is better than ours so it's getting attention. They are using ESAB Dualshield T-63, 100% CO2 @ 60-75 cfh to weld the same materials.
I was always taught that you do not weld through paint and this just flies in my face. Even ESAB does not recommend any change, stating that I already have their superior product. I do not want to make this change and I have some support for my stand but I am very interested in my fellow metallurgists and engineers positions on the concept of welding through paint. Thanks!





RE: Welding through Paint and R/P
Do you have any say in what paint your supplier uses? There are some supposedly weldable primers out there.
I haven't seen the following sources myself but they were brought up on an SSPC discussion list (I'm copying & pasting from old listserv email, with no permission whatsoever):
* SSPC-Paint 30, "Weld-through Inorganic Zinc Primer"
* Munger (Corrosion Protection by Protective Coatings, Second Edition) discusses welding inorganic zinc coated steel in detail (p 156).
* Nippe Ceramo (a kind of paint, I assume)
* discussion of "Weldable Shop Primer" in one of the SSPC red books, probably Good Painting Practice but possibly one of the specifications: 'for the most part it is up to the ship yards and fabricators to "self Approve" a coating as "weldable" based on supportive data received by the coating manufacturer, largely based on burn spread rates (how far weld burn-back spreads to either side of the weld), how thick the coating may be applied as a weldable primer, etc.'
If you can find an archive for the SSPC Coatings Talk list there might be more info there.
Hg
RE: Welding through Paint and R/P
The issue of welding over a coating needs to be carefully evaluated to assure consistent weld quality with the base material, and to assure the welders are protected from any harmful fumes that could be admitted into the air from the welding arc. If your sister company has gone thru and evaluated this risk, I see no reason why you can't use it at your facility, as well.
RE: Welding through Paint and R/P
Hg
RE: Welding through Paint and R/P
Steve Braune
Tank Industry Consultants
www.tankindustry.com