Factory frame coatings, What did they use?

[Black1990jeep]

I am looking at my XJ frame, both inside and outside of the frame rails. Inside is pretty, nice rust free silvery grey coating inside, very smooth, no signs of drops or such that would be expected if the frame insides got coated by dipping or a spray wand. I suspect the frame may have been coated prior to it being welded to the floor pan. The same silvery grey coating is on the outside of frame too, but under the top coat color paint and under coating.

What did the factory do here? Is this a galvanized plating? a zinc rich paint? Is this a weld thru material (i.e. if applied before the frame was attached to the pan, then it likely is a weld thru coating. or was the coating applied after the frame was welded to the pan?

what is this stuff?

thanks

 

[Jim Malcolm]

Yes, it is a zinc plating of some sorts. You will have a hard time welding through it.

 

[Unclewolverine]

I dont know what they put on mine but my jdm 95 has 0% rust despite being a 300k mail jeep in the midwest.