Which substance can damage a pipe to the point of opening a hole in the trap? I used two times that i remember Drano® Max Gel in the past 4 years
I believe you are talking about the p trap or U bend. The old metal drain lines do wear out because of acids in food, I know many years back I bought a place that looked good but the chrome plating was all that was left on some of the pipe it developed a small leak when I went to pull it it crumbled like an eggshell. Most of the modern drain cleaners won’t harm pipes. If the cleaner has acid that is a different story and the will damage pipes to tell the truth 2 times is probably not enough for even acid based to cause the problem, things like tomatoes and citrus have more acid in them than drano which is usually a strong base and is great at dissolving organic but really doesn’t hurt pipes. If the pipes are a shiny silver color they are probably chrome plated brass this is very common and what I have had crumble.