Rust stains on brickwork

[TheRoost]

We have a large rust stain on brickwork where the previous owners faulty boiler used to dump it's central heating water down the outside wall via a pipe.

The bricks are stock reds and have that nice 'industrial revolution' patina elsewhere, so I want to clean off the rust without inadvertently making the bricks look too clean/new or stand out. Has anyone successfully managed this using mechanical methods or chemicals of any sort?

I was thinking of buying a brass brush and trying that, a churn brush hasn't worked.

 

[formerly known as]

try lemon juice and vinegar. if you are able to soak a rag in it and attach this to the wall - lean a length of 2x4 against it etc - then this will allow the mixture to do its stuff. Have a look after 1/2 hr and give it a scrub. Coca cola would work as well, but this is quite sticky.

 

[Penners]

You may find advice suggesting that hydrochloric acid is the answer to this problem, but it is fraught with risks - not just to you but to the bricks, too. Oxalic acid is what the experts recommend.

But it might be best to start with some gentler treatments. The following website has some ideas, although I disagree with their suggestion that you should use steel wool. This will tend to leave small steel particles in the grain of the brick, which will then rust! Not exactly the solution that you're after! Likewise, don't use a ferrous wire brush.

http://homeguides.sfgate.com/clean-rust-off-brick-20546.html