There are chemical blacking gels and solutions available for stainless and for ferrous, but its difficult to see which one to try when you don't know what you have?
Hi Rob...Not all stainless is non magnetic...There are many grades with varying applications and characteristics..So, if the clips are marketed as stainless I'd go with the blacking compound produced for that material...
I tried blacking stainless with gun barrel black (blue) and it didn't 'take' at all...Ian