De Rusting Rear Calipers

[CallMeLegend]

Was wondering about the best way to derust the rear calipers I have. They have a light coating, was thinking of fully stripping them & immersing in Bit Hamber Deox C, it#svery good stuff, just concerned about the damage to sealing surfaces.

[Simon_P]

I use electrolysis for most things Soda crystals are a pound for a bag.
Various acids depending on what I'm doing and the green stuff in the white bottle (made by Hammeite) from Halfords or the gell version of the same stuff.

Cast Iron can be quite porous so consider what the consequences are of not being able to get it all off.

[dapinky]

I just strip them down and soak them in 10% phosphoric acid........ it is harmless to rubber, so you can use it without stripping them if you want to, but as I fit new rubbers etc as a matter of course, it makes sense to dip them bare, and then paint them with VHT black spray paint.

[CallMeLegend]

Deox C is basically Citric acid with some surfacants in it

[Rambo]

I wouldn't have thought citric acid wood do much. Phosphoric acid yes

[CallMeLegend]

I wouldn't have thought citric acid wood do much. Phosphoric acid yes

Good Bilt Hamber Deox C. It is literally magic

[Rambo]

I've got some OEM front and rear calipers in my spares box. Must try it

[Brit-Car-Nut]

Once cleaned, reverse the process with a dunk in some lemon juice.

I didn't read this but it seems to be a decent way to safely clean metal and then stabilize it.

https://homearise.com/neutralize-vinegar-metal/

They feel clean water is enough to stop the vinegar. Just be sure to paint or otherwise coat anywhere that will be exposed to the weather once they are dry.

[dapinky]

They feel clean water is enough to stop the vinegar. Just be sure to paint or otherwise coat anywhere that will be exposed to the weather once they are dry.

I think I'd want to use a dilute solution of Bicarbonate of soda to neutralise acetic acid (if only to stop the car smelling like pickled onions when the brakes get hot).

Not sure of the chemistry with Citric acid - but it's fairly harmless stuff generally.

I'll stick with Phosphoric though, because I understand the chemistry with it, and if you don't wish to paint it straight away, no great problem as you will leave a coating of Iron Phosphate on the surface of the steel (or cast iron) which will prevent further oxidation..... but I don't know how long for, so tend to paint pretty much straight away whilst the acid is still acting as an 'etch' on the steel.

[Rambo]

Citric acid is a fairly weak and tame organic acid so using water as a washdown in the process is probably OK. I would put the calipers in a warm oven before painting

Citric acid is also less harmful to the environment

[Simon_P]

I thought that must be the most expensive way of buying citric acid known to mankind......but I just checked and the Hammeite stuff that I use (which is excellent) is also citric acid based and just as expensive!

Citric acid powder looks cheap enough anyone know what mixing ratio is most effective for rust removal?

[Rambo]

Try 15g per 400 ml warm water. This is ~ a 4% w/v mix so if it's not doing much on a test piece ( try an old saw/rusty plane or set square) increase the conc'n

PS wear disposable gloves as it can sting if you have a cut on your fingers. Also advisable to wear safety specs in case of a splash.

[rob/d]

Phosphoric acid , with gloves and goggles on , paint on and off with a paintbrush .

[lotusflasherman]

I wouldn't have thought citric acid wood do much. Phosphoric acid yes

so said the chemist who is taking too much Viagra - problem with 'wood'
(Blame it on 'autocorrect' .. )

[Rambo]

I wouldn't have thought citric acid wood do much. Phosphoric acid yes

so said the chemist who is taking too much Viagra - problem with 'wood'
(Blame it on 'autocorrect' .. )

Ha ha Phil. I didn't spot that one

PS I'd get some blue pills if I could but the Dr said they're in short supply due to an over indulgence in the Ipswich area