I see this substance is being discussed to clean off rust and other crud off metal. I want to offer this cautionary tale. About 30 years ago I was using it to clean a pair of 18th Century andirons. I was in the corner of a basement. Feeling that the fumes were getting pretty strong I got up top go outside and take a break. When I stood, the whole place spun and I just dropped to my knees. I realized right away (One might not) what the problem was and crawled away on my hands and knees to the basement stairs and beat a hasty retreat to fresh air.
When using just about anything that is strong, be sure you have both ventilation and probably a mask, too. Safety glasses and gloves are a must with anything of this ilk. Lots of legal stuff (from chrome polish, to oven cleaners) can be dangerous under the right circumstances. Be very careful.
Tom Sanders
Lansing, MI USA