tbh... if your using vinegar.
Careful
it may only be weak acetic (ethanoic) acid but I remember doing experiments with that stuff in school at GCSE. It will eat the magnesium.
Make sure you swill any solution out well afterwards with water.
Oxalic acid is the bigger brother of acetic acid basically. Two -OH groups as opposed to acetics one.
Its more reactive, and if its concentrated stuff and not diluted expect it to eat away the magnesium in a shorter time
Careful with it!