Welding repairs and old undercoat

A common situation discussed with my current project includes rear torque box and spring hanger repair.

Not often discussed is related common problem of heavy old dried tarry undercoat .

Suggestions appreciated how anyone's dealt with this reasonably for panel/subframe repairs.

... Need to clean adjacent steel to weld to new steel . I've used bonding as well as stitch welding for panel repairs and structural subframe/spring works best with good clean weld surfaces.

thanks

 

I have been using a needle scaler, works amazing on the stuff that is set up and hard. It isn't the best on the gooey stuff, just seems to move it around.

 

I lucked out and it was a cold day when I did mine with a needle scalier and it all came off...

 

I have used a gasket scrapper and a hammer.

 

I borrowed a high end heat gun from work and heated it up and it came right off with a putty knife

 

I was reading that if it is in an area that you can apply dry ice to it from either the top or by laying the ice on it it almost falls off . Seems like there would be far less mess than heating it up . If you were able to use a can of compressed air sprayed on it with can upside down that would freeze it as well

 

.. thanks for replies. Never simple solution but likely use a few different methods in different places and needed tips and encouragement.