Weld through Paint

[side-show-bob]

Hi all

I have been reading some threads and they make reference to a paint which you can apply before welding and then weld through it. What is it and is it any good?

Cheers
Rob

 

[Rich.C]

Rob,

Bilt hamber do a weld through etchweld http://www.bilthamber.com/etchweld.html I have not tried it myself yet but have used some of their other products which have all been excellent.

Cheers,

Rich

 

[peterd51]

Hi,

there's also some spray on stuff that stops spatter sticking.

Someone gave me a can to try once, made by Murex I think, not sure of the exact name but I can check tonight when I get back to my workshop.

I don't use it on the workpiece so much but an occassional spray into the torch nozzle helps to stop the wire sticking if I get a burn back (due to my dodgy welding style usually!).

Regards
Peter

 

[TechnicAl]

Its called Weldable Primer. Even then its only weldable (without defects) if its thin enough. There are a number of brands International Paints do one called Nippy Ceramo and Tempil make Bloxide which is probably the best but the most expensive. Hempel also produce one but I cant remember the name.
They are used by Ship Yards etc so the steel has some protection during building.

 

[malcolm]

Is the protection only before welding? I've not used the stuff as I'd imagined it would burn off in the heat affected zone which is the bit that rusts the worst. I tend to go for bare metal in the joints and attempt rust prevention later.

 

[Drains]

Is the protection only before welding? I've not used the stuff as I'd imagined it would burn off in the heat affected zone which is the bit that rusts the worst. I tend to go for bare metal in the joints and attempt rust prevention later.

Protection only until welding, absolutely.

These primers are normally known as "holding" primers. They are weldable, generally, if thin enough (put on thickly, forget it). They provide a very temporary, short term protection against rust.

Anything welded MUST be painted immediately, especially if left outside, unless you want it to rust, or you're prepared to go in later with the wire brush/grinding disc.

Si

 

[Hitch]

When you buy steel from larger suppliers, they will give you an option of shotblast and paint.
We get most of our stuff thats not going for galv blasted and painted. Its all done in one machine. The paint is sprayed whilst the metal is still warm from blasting, and some also have gas driers.
Its a thin coat, enough to protect the steel for a few weeks (longer, but deteriorates after a while) during transport, storage, fabrication....
Ideal for structural steelwork- just prime the welds, then paint

 

[TechnicAl]

The bloxide can be welded though regardless of thickness (I suppose there is a limit) because its Aluminium Oxide base whilst the others a Zinc Silicate based and will form porosity if applied too thick.
The Bloxide is very expensive though.

If its a big issue, there are steels known as WEATHERING steel which provide some rust resistance. They are usually called CORTEN and they conatin small amounts of Ni, Cr and Cu and you can get MIG wire that is similar. To be honest they still go rusty but its only a thin layer and it stays the orange colour rather than go black and drop off. There are a lot of buildings made from this stuff and they look as though they have been painted but its the bare steel. The Angel of the North is made from Corten.

 

[irondarren]

That corten is freaky stuff, goes rusty (sort of) then the so called rust provides a protective barrier, to stop more rusty. chip off the surface coat to show bare metal again and it reoxidizes again to protect itself. unlike mild steel that surface rusts then the rust goes deeper and eventually makes it start to laminate, under the surface of corten, its always clean steel