One possible
problem, Sodium Hydroxide < .5% could be damaging and
corrosive to metalic parts.
About the only common material that sodium hydroxide will attack is
aluminium, and then only when concentrated or exposure is reasonably long;
it has no effect on copper, steel, etc.
Yeah, I've relied on this as a way to make satin-finish aluminum
front panels for equipment. As the reaction progresses, the NAO2 (?)
solution has to be preiodlically replaced. It generally took me about
two days to get the desired look.
-dq