Removing rust stain from tiles?

[UTH]

Annoyingly our metal umbrella has left a couple of rust stains......is there a miracle chemical that will get rid?

[CharlesElliott]

Iron fallout remover (as used in car detailing).

[JoshSm]

Zep Calcium, Lime & Rust Stain Remover, available from lots of places, or any similar cleaner with phosphoric acid.

Can also try citric acid which is what the fallout remover often is.

[UTH]

CharlesElliott said:

Iron fallout remover (as used in car detailing).

Ahhhh nice, got some in the garage will give that a go

[UTH]

JoshSm said:

Zep Calcium, Lime & Rust Stain Remover, available from lots of places, or any similar cleaner with phosphoric acid.

Can also try citric acid.

If the above fails, will give this a go. Thanks

[UTH]

UTH said:

CharlesElliott said:

Iron fallout remover (as used in car detailing).

Ahhhh nice, got some in the garage will give that a go

Bingo, worked perfectly. Nice one

[CharlesElliott]

Great! Were you temporarily worried when you had large purple stains all over your patio?

[UTH]

CharlesElliott said:

Great! Were you temporarily worried when you had large purple stains all over your patio?

Haha, no, relieved to see that, now I know what it does.......the first time I used it on my wheels was a shock though, many years ago.

[gotoPzero]

As it would happen I am in the middle of doing a test on render between dragons breath and bar keepers friend.... will report back!

[JoshSm]

gotoPzero said:

As it would happen I am in the middle of doing a test on render between dragons breath and bar keepers friend.... will report back!

Bar Keepers Friend is basically just oxalic acid which used to be easy to get for cheap. Now oxalic needs an EPP licence for anything except the dilute solution which is a weird & annoying situation. Oxalic was great at eating aluminium oxide and copper oxide too.

Strong-ish phosphoric acid is also in the same boat of needing an EPP licence, great safe rust remover as it doesn't disolve iron and in theory coats it with phosphate.

Citric acid is a pretty benign descaler/rust remover that you can still buy in bulk for cheap, useful for many things & friendlier to some materials though doesn't self limit on iron (which is why it works to clean/passivate stainless). Also eats copper oxide which can be handy, and passivates copper metal.

[gotoPzero]

Bar keepers friend is on sale at Home Bargains - fwiw. I bought several bottles.

The results...

Dragons breath. Brushed on neat with a stiff brush. Left to activate 5min. Agitated again. Rinsed. Removed 50%.

BKF. Made into a paste, brushed on. Left for 1 min. Agitated with stiff brush. Left for 2-3 mins. Rinsed. Removed 95%.

This was on white render. I think if I had left the BKF for 5 mins or maybe a bit more it would have been even more effective. I was worried about damage to the render.

[JoshSm]

gotoPzero said:

I was worried about damage to the render.

If it's fizzing a lot that's usually a clue about how much it's doing to the render.

Oxalic/BKF can produce some interesting coloured insoluble byproducts (yellow stuff) in my past experience.

Phosphoric is pretty active stuff but *generally* doesn't stain, though it will merrily etch.

If it doubt go dilute and trade time for control.

[Chucklehead]

Lithofin Rust-Ex worked well for me.