how much citric powder /ratio

[fizzy]

I use pure citric acid in hot water. And 47 percent caustic. Removes just about everything

You always get results mere mortals can't achieve
That is a lot of caustic to add to a weak acid - what ph are you getting?
Yours is definitely a chelating process.

 

[fizzy]

ive gone from being really pleased with the first overnight results to a bit miffed , the last specs wont shift after another 24hrs

ive rattled over then with wire wheel /60 grit , scrubbed with washing up liquid and put a bit more citrus in

You can always give any stubborn spots a quick rub with a brush whilst it's still in the mix. Not had this problem myself.
Remember things need to be very thoroughly degreased before placing in the bath - and obviously any remaining coating needs to be removed.

 

[steveo3002]

You can always give any stubborn spots a quick rub with a brush whilst it's still in the mix. Not had this problem myself.
Remember things need to be very thoroughly degreased before placing in the bath - and obviously any remaining coating needs to be removed.

the stubborn bits just wouldnt go ...you know where its gone so far flakes come off , i had a couple of areas with like a cornflake size bit stuck on , time ran out and i manually tickled them with a dremel

next time degrease better , and give it a good shake down with a wire wheel etc before trying

i did try a brake disc thats laid in the garden for a year a soak and it derusted that in hours

 

[RichardM]

Just to confirm that quantity, its 100g per liter of water for the citric and 40g of soda crystals?

And a little squirt of washing up liquid as well.

 

[Dapph2]

Fizzy , did you manage to re- constitute the solidified gum de-ruster into a thinner substance for painting it on?

 

[fizzy]

Fizzy , did you manage to re- constitute the solidified gum de-ruster into a thinner substance for painting it on?

Not yet been too busy.