The cleaning forum might be more appropriate for this but I figured more "ACL" eye's would see it here. I have cleaned oil cans with good success using Oxalic Acid so was very curious to see if it would clean rust off a ACL bottle.I call it rust as I have seen others call it rust, but more likely just a mineral stain?I had already soak this bottle in hot water and sunlight dish soap previously and could not remove the stains or the stubborn clouding on the inside of the bottle. The bottle soaked for 3 hours with light scrubbing using a tooth brush every 30 minutes.I am very impressed with the results, I did notice that the paint in the area where the stain was has lost some gloss. But you can't tell unless looking close and gun sighting it. After I had finished soaking the outside I poured the water/ Oxalic mixture into the bottle. I let it sit for 30 minutes with out scrubbing, just rinsed it and it removed the film from the inside. I have a Sparkling bottle now! Have a look at the before and after pics, also a pic of the bottle soaking.