Welding on deeply pitted rusty metal

[BWSwede]

Greetings all,

I need to make a structural repair to my tractor. The area is probably about 12 ga, maybe slightly thicker, steel and is deeply pitted. I have used an abrasive wheel to clean the surface down to clean metal but obviously this doesn't work in the pits. Is there a chemical treatment I can use that won't harm the good steel but will eat the rust in the pits that will, in the end, allow me to weld over it?

I have heard muriatic acid works well to clean metal but due to its chemical properties the steel keeps rusting long after the acid is removed.

TIA,
BWSwede

 

[davesl708]

I was at the hardware store yesterday and saw a product that is supposed to stop the rust from progressing.
Might work for what you are doing.

Muriatic acid has to be stopped after you apply it or it will keep etching.

 

[s219]

Naval jelly?

 

[pmsmechanic]

A mixture of 1 part molasses to 8-10 parts water does a very nice job of cleaning rust off to bare metal. You need to submerge it for about 10 days or so but it works. No harsh chemicals to deal with after either. Just wash off with water and dry and paint or weld or whatever you want to do.

 

[bikerdib]

Have you tried a wire wheel or wire cup?

 

[BWSwede]

Thanks for the replies guys. I read that naval jelly's active ingredient is phosphoric acid. It converts (not removes) the rust to iron phosphate. I am just not sure how well a person can weld over iron phosphate. It seems to me the phosphate portion is an impurity and would lower the quality of the weld, if it is even weldable.

BWSwede

 

[sixdogs]

Have you tried a wire wheel or wire cup?

This is a good idea followed by some sort of light grinding.

The better the prep work, the better the weld and I always start with a good amount of clean steel. I'll just presume you are using flux core wire or stick because those will tolerate some unclean metal.

 

[arkydog]

i'm not a welder, but i would think if you got most of the rust off, and then use a welding rod for rusty metal like 6011 or 6013 can't remember, it should work just fine. i have done it with great success.

 

[Egon]

Posphoric acid will get to the interstitial rust you can't see. Apply it and then clean area with wire brush etc.

 

[dickfoster]

Naval jelly?

What he said. It's a weak acid suspend in a jelly so it will stick to the metal. After it has done it's work, clean and neutralize then get on with what you were going to do with the steel.