Acid rust removal

[bigdaz]

The bottoms of my rear doors had quite a lot of surface rust on then but as there lots of nooks and crannies using a wire brush would of been a nightmare, so with a bit of research I thought if I get a plastic tub big enough to submerge the bottom few inches of the doors and use phosphoric acid I could remove the rust much easier, so I got a plastic tub from a cheep shop and the acid from eBay
Which was 85% acid and £18 for 5 litres, I diluted it with 5 litres of water and wow in two hours 90% of the rust is gone and back to good metal I'm absolutely amazed when it's finished I'll put some photos up,

[darrenh]

sounds pretty effective, but will it have stripped any protection between folds/lips where you now cant replace it ?

[93fxdl]

The downside to dipping can be the acid seeping back out of joints later, and causing rust, just make certain you get rid of all traces of acid when you finish.
Ttfn Glenn

[colnerov]

Hi, As has been said be aware that it gets into folded joints and causes problems. In TonyBMW's thread on the FB Victor he had to revisit some doors corners which erupted again later after being dipped.

Colin

[composimmonite]

Phosphoric acid leaves behind iron phosphate which has anti rust properties.

[bigdaz]

If I would of left the door it would need replacing soon so
This seams like the best thing to do, and as long as I dry it off properly and paint it straight away I think it will be ok,
There are a few small holes in the outer skin but I'm sure the welder who's having the car in a few weeks will be able to sort it,

[bigdaz]

And after that's with four hours of soaking

[shin2chin]

That's what I always use too, 5l bottles from Ebay at around 80%. It's the active ingredient in most proprietary rust converters I believe.

[bigdaz]

I hosed the door off and left it in the sun to dry and the was no flash rusting so I'm confident all will be ok

[DavidB]

Use (I think) bicarbonate of soda to neutralise the acid.

[shampooefficient]

Does pumping Waxoyl* into the seams have any effect, or does the acid, being thinner, still find its way through?

*more modern anti-rust treatments are available

[quackshot]

I have recently used oxalic acid which works VERY well.

Before:

Really horrible oxidisation


After:



£10 for 1kg of oxacylic acid
£15 for 150L container from homebase
Added about 25l of hot water, and stir well. Add your metals and cover.

The acid can be re-used but I havent found a suitable method of filtering it yet

[colnerov]

Anyone know what the score is with disposing of it is? Down the drain?

[quackshot]

Jul 21, 2016 9:50:35 GMT colnerov said:

Anyone know what the score is with disposing of it is? Down the drain?

Not advisable

[colnerov]

Jul 21, 2016 15:10:27 GMT quackshot said:

Jul 21, 2016 9:50:35 GMT colnerov said:

Anyone know what the score is with disposing of it is? Down the drain?

Not advisable

Yeah, I thought not. I'll stick to electrolysis because that can.

Colin

[quackshot]

Jul 21, 2016 20:47:03 GMT colnerov said:

Jul 21, 2016 15:10:27 GMT quackshot said:

Not advisable

Yeah, I thought not. I'll stick to electrolysis because that can.

Colin

I've started using the left over stuff to clean my patio after making it so grubby with car stuff. A good rinse after, it is water soluble.

[dodgerover]

Jul 21, 2016 9:50:35 GMT colnerov said:

Anyone know what the score is with disposing of it is? Down the drain?

Most one shot drain cleaners are concentrated Sulphuric acid used neat, I cant see too many issues.

[kevins]

Jul 20, 2016 18:40:16 GMT shampooefficient said:

Does pumping Waxoyl* into the seams have any effect, or does the acid, being thinner, still find its way through?

*more modern anti-rust treatments are available

In my experience waxoyl is pretty poor at creeping into seams I usually add a little (approx 25%) new engine oil to it then creeps much better but still seems to set after a few days, some of the modern alternatives have water displacing properties which should work for acid as well. I would suggest the best option would be to try to neutralize it chemically then low bake the doors.