Calliper De-Rust Comparison. Electrolysis-Acid-Molasses-Vinegar.

[Zebbysebby]

Five weeks ago I began an experiment to find out what is the best way to remove rust from Brake Callipers ahead of reconditioning. Obviously other parts can be used but Callipers, rears in particular can be difficult to clean up with a wire brush and I wanted an easier method.

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Molasses and Vinegar.

Priced at around 90p and 60p a litre respectively, the Molasses I obtained came from Harbro in a 10 litre container. You need it to still contain Sulphur. De-sulphured Molasses won’t work I understand. The Vinegar was standard Supermarket white Vinegar.

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Both Callipers have been suspended in solution for four weeks and the results are in.

Vinegar.

Sadly very little to see but it has had a slight effect, I suspect with more time possibly another two months it might do the job.

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What I didn’t like was the corrosion which appeared inside the piston housing, this isn’t flash rust. All of the internal section had a thin coating of fine rust dust which wiped away to reveal this.

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I decided not to carry on with vinegar but it would work over several months, maybe not use it on any items with a finished face or a required tolerance.

Molasses.

This actually worked quite well. Another 2-4 weeks would be required and from what I could see the surface looked undamaged by the process. This was the only method that left the Calliper with a metallic look, the other three methods left a brown appearance.

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I used a tub with a lid. I understand that if a lid isn’t used then mould will grown on the top. I have put this Calliper back in for another four weeks.

Acid.

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Costing around £1.20p a litre, the Acid initially worked well but began to struggle with heavy deposits so eventually it spent 10 hours in liquid. It left the surface looking pitted but possibly this is mostly down to years of corrosion on the car. This for me is still a good method to be used on Calliper Carriers but any built up rusty sections will likely need hammering off before or afterwards.

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[Zebbysebby]

Electrolysis.

This method may sound complicated but is actually quite simple and effective. I would advise first reading the write up by TBJ before trying.

I used a basin, (approx 6 litres), With about 200 grams of a 1Kg packet of Soda Crystals costing £1. TBJ advised 1Kg:85 Litres of soda to water so this should be plenty. I wrapped the Calliper with copper cable cut from standard 2.5mm grey Twin and Earth cable and connected it to the negative side.

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I wrapped the copper around my sacrificial Anode, an old steel trailer pin, connecting it to the positive side of my charger. I didn’t have any plate lying around which I understand is better.

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I tried using a fairly modern charger with a 2 amp slow charge function however the unit didn’t switch on, possibly it detected a fault so I used my 38 year old British made charger.

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It started off at 1 amp and slowly rose to 1.5 amps. I could see Hydrogen bubbles coming off the Trailer Pin and a visible effervescence around the Calliper.

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After 17 hours the Calliper was mostly clear of any rust but there still were a few problem areas especially the curve inside where the copper hadn’t made contact. These were chipped off with a hammer. Surprisingly there was rust inside the Piston housing.

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The positive Copper wire connected to the sacrificial anode, (S’ Anode) is eroded during the process, it felt thinner and more pliable. This wire may have lasted another 24 hours.

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I decided to use the Electrolysis to finish off the Calliper which had been dipped in Vinegar. This time I wrapped it in copper wire considerably more than the previous one. This time I started with a clean solution in my basin using about 300grams of Soda and a new Anode copper wire. The trailer pin was cleaned of all rust with a grinder. The charger started at 2 amps.

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This was the result after 15 hours. It appears the extra copper wrapping didn’t make a lot of difference if any. Most of the rust seen still on the Calliper will fall off when wire brushed.

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[Zebbysebby]

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Had I left it in for the full 24 hours it would likely have remove the last stubborn pieces.

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Verdict:

For speed, Acid gives the quickest result but can cause pitting and needs to be monitored closely. Molasses appears to work well and seems to be kind to the surface metal but will need around two months. Fine if you’re not in a rush. Vinegar will work over a long period of time but I won’t be using it again. Electrolysis works well but needs to be completed outside due to the Hydrogen Gas released during the process and therefore you need to be mindful of the Weather, animals etc. That said, I do know people do this inside their Garage, I suppose it comes down to ventilation.

I have four more Callipers for reconditioning which I’m in no rush for. I think I’ll put these in Molasses and forget about them for two months.

I bought another car recently which also needs all the Callipers reconditioning so I’ll use electrolysis for these just for speed and I’ll dip the carriers in acid for two hours.

I also have a front Wishbone which I was keen to try Electrolysis on. Using a larger container with around 30 litres of Water. I used the remaining 500 grams of Soda.

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The charger started at 2 amps. As the Rust is removed onto the S’ Anode the charger appears to drop. I ended up cooking this Wishbone for 40 hours, the S’ Anode was removed and cleaned twice. Right after this the charger would return to 2amps. At the 40th hour it was down at 0.5amps.

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I found this swimming about in the rusty water. Seems to have been unaffected by it.

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This is the result, there is still some heavy deposits but most of the rust still attached will fall off when wire brushed.

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After rinsing and wire brushing I immediately dry with a Propane Gun to avoid flash Rust. This Wishbone still had its Rubber bushes which appear unaffected by the process however the plating on the bush sleeves has gone.

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The Copper wire was still OK after 40 hours but I won’t be re-using it.

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So, there it is. Not too difficult and not hard work. Wish I’d tried this years ago.

[Zed.]

I use phosphoric acid solution now, have a plastic 200L drum as a soak-tank

recently dipped a cylinderblock





and wishbones



thats 10L of 40% phosphoric in ~150+L water




I have used vinegar (aldi or lidl) & el-cheapo diet cola ( tesco's) both mixed & neat as rust removal, the cola has phosphoric acid so this eats the fe02.

Rich.

[Zebbysebby]

It seems my comprehensive test is missing something , honestly I didn’t know about Phosphoric Acid but I’m curious now. I have seen that it’s about £25-30 per 5L.

I also saw it is to some extent bio-degradable, re-useable and gives some protection against re-rusting so it should be considered.

I’ll have to obtain some myself and see how it compares to Hydrochloric.

Might also have a go at the Vinegar and Coke and see how effective it is but suspect it won’t be quick.

Thanks for the advice.

[Zed.]

Phosphoric acid?
used as cleaner, food additive & de-rusting

when you've finished with it you can pour down the drain & know the drain will be cleaner afterwards

I bought
https://www.ebay.co.uk/itm/Phosphoric-A ... 2749.l2649
£43 posted for 4 x 5L cans.
beware though as it's sorta strong & will 'burn' skin. (even diluted will 'sting' )


anyway, vinegar...

one bucket, add a diff 'pigs-head' & drown in vinegar...

leave soak a day or two, maybe agitate...

insert into 'partswasher'* and polish with a rotary brush on a drill...

heat & spraypaint with satin-black paint...

build diff using Kia Sportage 4.778:1 crownwheel&pinion

Rich.



* Dishwasher, helps if you have an understanding mrs (also a mrs thats a petrolhead )

[Zebbysebby]

Thanks for the info...will try and get a small amount first and see how it goes. Have noticed that the Hydrochloric looses strength after the third use and disposal isn’t straightforward. Interesting idea about using your Dishwasher as a parts washer, I’ll let you know how that suggestion went down.

[Mazda Mender]

Acid with a phosphoric is a good rust eater..but we do have a rust restore fluid which is great stuff that i use...i'll find out whats in it..?
M-m