Is acid rust converter safe to use on frame? (1 Viewer)

[MarkBC]

I got some replacement c channels from @TRAIL TAILOR. There is some swelling there and I want to treat the rust with ospho or por metal prep. But trev's blog on youtube says not to use acid on anything structural because of hydrogen embrittlement. But he was using citric acid, not phosphoric acid. Is this a problem?

 

[fl4031003]

Should be fine, I don’t have the rust issues you have up there but I use the stuff all the timr

 

[OSS]

Ospho (phosphoric acid) won't really help swelling rust because the oxidation has eaten all the way through the steel. What you're seeing when looking at swelling rust really isn't steel anymore but an intermediate form of soil. There's more oxides of iron than iron.

If a section of bloated frame was cut out and dropped in an electrolysis bath to remove all rust, there'd likely be only just orange sediment left in the bottom of the tub after a week... with no frame left in sight.

No acid brushed on (Ospho) is going to be able to penetrate grossly bloated rust. It'll just treat the outside surface. Being so, there's no way to really stop bloating rust from doing what it does best:,turning iron into dirt.
Rust contains moisture inside its rust cells and attracts more moisture like a sponge just from the humidity in the air.

I've used Ospho extensively on all my rusty parts prior to painting and I it definitely works well, but I don't think it'll do much for bloated rust

 

[MarkBC]

I think it swells because iron oxide has more volume than iron so it pushes the metal apart. It looks like there's plenty of good metal there, I'll find out when I cut out the bad c section. I was going to grind away most of the rust, was just hoping to use acid to loosen the rest to get me down to metal.

 

[MarkBC]

I took off the spare tire cross member and ground off most rust and I'll soak it in an electrolysis bucket to finish it off. Wasnt too bad.