I recorded a short clip the other day of making bare steel rust quickly by using diluted brick cleaner, followed by water. I let it run in real time so folks can see how quickly it works. I have used diluted vinegar in a similar way before but it makes your work stink and attracts every wasp within a mile. Rust is a popular finish with folks in this neck of the woods and as I had to deliver some sculptures to a show that afternoon I needed them rust quickly.

 

Salt and peroxide works well to accelerate rusting. What's in brick cleaner on your side of the pond?

Frosty The Lucky.

Hydrochloric acid with Phosphoric acid.

Hydrochloric on it's own work just as well and is cheaper.

Dilute 10:1 ... add acid to water slowly, and not the other way around. 

I’ve used salt, vinegar, peroxide mix quite a bit, cheap and simple.  Recently though I’ve been experimenting with light spray of peroxide, followed by literally salting the work (using a salt shaker), then spraying peroxide again.  Works great.  

Thanks for the video, I love seeing real time rust, people don’t believe me when I swear I can make things rust instantly!

Concrete/brick cleaner here often says "muriatic acid" which is just low grade HCl (more contaminants).

Haha to be honest I've never looked at the back of the container. It's £7 for 5L of Cementone Brick and Patio Cleaner. No idea how that rates in comparison to the stronger acids, but the appeal for me of this stuff is I can just stop on my way to work at a tool shop and pick some up. I read somewhere for the stronger types you need to buy at specialist places and prove you reasons for use? Possibly a load of rubbish but lingered in my mind anyway. I use it so infrequently I think in 2 years I've only used about a litre.