T-Rust by bridge point is outstanding and works on contact with carpet. I have used it for years and years and would not use anything else. Just make sure you rinse it out real well.
So I would suggest that you could buy that with confidence.
Also, I would suggest you bump your price to 25 cents per square and include the rust and stain removal and anything else needed to
clear the room for cleaning. Don't' be afraid to sell the job for more, it is worth more. You can educated them why it is worth your charge.
It does not matter what they can do in house, if they could and would, they would not be calling anyone from the outside.
Also........I have the novel rust removal too. it is expensive and I use it
to get the toilets Crystal clean from black and rust. and the tubs from the black stains.
I don't have to scrub and it dissolves it like nothing else I have ever seen.
Just ware a good pair of protective gloves. It is very corrosive. In fact some of it leaked out on me in my bag I had my cel phones is and it destroyed them. So.......put it is a safe place and use it with caution.
But........it works. and if something works, you use it and you charge for it.
Does anyone know where you can get it for less than $25.00 per bottle.
Let us know how it all worked out for you.