rust removal/welding question, how much is enough? Options

[dkos]

Hoping some of you experienced welders can help me.

I know the surface you are welding to should be clean and rust free, but I'm wondering just how rust free? If I remove the loose rust and grind down the area, but there is still some pitting, can I weld to it? Do I have to grind it down to smooth shiny metal? If I Metal Ready the pitted area can I weld to it? If there is only some surface rust is it sufficient to wire-brush the surface rust and treat it with Metal Ready?

I've seen, in this forum, where people will paint the pieces they are welding with weldable primer. Sometimes they even paint the piece with POR 15. Won't this just burn-off when you weld?

Thanks for your help.

[tat2dphreak]

paint the new piece wih weldable primer.

grind down the old piece to shiny, not pitted... then weld... if you have to grind a lot(1/2 the thickness of the metal or more) then cut just back farther... you want to be welding to good metal...


I'm not sure about metal ready and POR-15, I dunno if they are weldable... metal ready should be, since it should be mainly a converter... but I dunno for sure

[Mueller]

I'd have to say depending on the part, it'll have to be a judgment call, remember that due to the rust will have caused the sheetmetal to be thinner...the thinner the metal, the easier it is to blow a hole right thru it with the welder....

you might want to shoot for lets say 75-80% of the original thickness

if you remove the rust and you have 50% of the original thickness material, it might be wise to replace it

[dkos]

I was afraid you were going to say that...back to the grind....

any tips on getting into corners?

[Dead Air]

POR-15 emailed me back a few weeks ago and said that welding turns POR-15 to ash, But I was wondering if would harm the weld, NOT the paint!