What rust converter really works?

[Master Of Puppets]

Now that Hydrate 80 appears to be no longer available I've tried a couple of other options (Ferro bet, Fertan etc) and
none of those have truly killed the rust. Now I'm not talking about heavy rust I'm talking about mild rust on calipers and carriers
that I have used sanding discs and wire wheels on, but there is always slight pitting where tiny bits of corrosion remain
and it's into those I've applied the above mentioned products, to which it initially looks to have worked by turning the pitting black,
but after a couple of days drying you can then take a Dremel bit to them and expose untouched brown rust underneath
the black.

Even after rust converting, priming and then painting them there is spots of corrosion appearing within a month where those small
shallow pits are, so the products I've used are not even effective on corrosion that is less than half a millimetre deep on pinhead sized pits.

So any recommendations on something that truly can convert shallow rust and not just blacken the top surface of it?

[LennyM1984]

Neat Screwfix CLR works for me. Works quickly too!

[SHutchinson]

Have you tried ordering it from the Bilt Hamber website? It seems in stock there, certainly it lets me get as far as checking out.

[Grenadier_45]

If you want the rust genuinely gone, Bilt Hamber Deox Gel or Deox-C. Astonishingly good, but takes time to work. If you're in a hurry and have an ultrasonic cleaner that the calliper could be dunked in, then put it in that with a solution of Deox-C. For either method, expect to take toothbrush/dremel with attachment and clear the top surface and repeat. That stuff will eat the rust out of the deepest pits if you let it. Just use a decent zinc paint when you finish before you paint over your finishing coats.

[scz4]

Lookup AquaSteel, originally designed for the maritime market. I've been using that on a recent restoration project. Very reasonably priced too.

https://aquasteel.co.uk/

[Belle427]

I personally think after years of trying them they are all rubbish, im trying this at the moment on some underbody type stuff so will se how it goes.
Removal is the only long term solution but thats not always possible.
https://www.rust.co.uk/product/phos-kleen-b-rust-r...
Bilt Hamber deox gel is another worth considering.

[ATG]

What problem are they actually trying to solve? The mere presence of rust does not create more rust. Bare steel, water and oxygen creates rust. So if you can seal rust under a material that doesn't allow more water of oxygen to reach the underlying metal, then it isn't going to rust further. I'm guessing the problem is that rust stops most paints from bonding and creating that seal, so you either need to remove the rust or apply some gunk that mechanically stabilises it so that paint can then form a reliable seal.

You often hear people talking loosely about rust spreading and suggesting that failing to fully remove rust dooms you to having the rust return as if rust creates more rust, a bit like how fungus spreads through a bit of wood, but I don't understand how the chemistry would work.