Did some experimenting last night. Mixing 15:1 like the bottle said will not touch rust stains. So, I tried 1:1 on a couple different spots. The first was on my driveway where I have some light rust stains. While it did remove the rust, it also turned the spot a whitish color. So, I etched the concrete, but it probably wouldn’t have been so noticeable if I pressure washed it right away. Since I was just testing, I didn’t have much in the way of rinsing lined up. I basically put it on, dwelled a few minutes, brushed and poured water on it to rinse. It doesn’t look bad, but it’s noticeable. I’ll try 4:1 and do the whole area and blend it in. Actually rinsing well this time.
On my white trim, I have a spot where there was a metal hook screwed in and it left a rust stain that runs down about 2’. It’s been there since I bought the house 7 years ago. I was amazed and how this stuff just made it disappear in about 20 seconds. Sprayed it on and just watched it disappear from the bottom up to the worst part. I hit the hook itself one more time, and within a minute it looked like brand new. Best part is, it doesn’t look like it did anything to the paint or the siding that I got some overspray on.
I’ll keep experimenting before trying it on any customer’s homes, but for rust on trim and siding, it looks like a great alternative to BARC or OX. Just not sure about using on concrete yet. It was $29 for a gallon and it only took about 3-4 sprays mixed 1:1, so this gallon will last a while.