You can buy 85% phosphoric acid on ebay for about £14/litre. This would make over 3 litres of 25%. I submerge all removed steel parts in 25% overnight. After rinsing they present a grey coating of iron phosphate that inhibits further rusting prior to painting. Although you need to take care with it, phosphoric acid is not a dangerous acid like the main mineral acids, sulfuric and nitric hydrochloric etc.
 
You can buy 85% phosphoric acid on ebay for about £14/litre. This would make over 3 litres of 25%. I submerge all removed steel parts in 25% overnight. After rinsing they present a grey coating of iron phosphate that inhibits further rusting prior to painting. Although you need to take care with it, phosphoric acid is not a dangerous acid like the main mineral acids, sulfuric and nitric hydrochloric etc.

Much appreciated. I will look into this as the vinegar is taking it’s time with the bits I have in there.
 
Right........

After 2 weeks.......

A quick clean over with wire brush .....

Taaaa daaa

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Had one or two lumpy bits of rust still on , but fell off when tapped with hammer.

Not sure if 2 weeks was too long.....calliper metal seemed to have a softness to it as I was wire brushing.

Still, a good experiment.
 

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