Identifying Monel From Stainless

Has anybody heard of using Nitric acid to identify Monel from Stainless. Supposedly a drop of Nitric acid applied to a small area on Stainless will result in no colour change but if applied to Monel it reacts with the copper content and results in a greenish hue.

 

I would think it pretty hard to tell visually on monel wire or staples but a larger piece should have the slight green/yellow tinge or hue to it. Some people have plated m/cycle frames in nickel so if your familiar, that is the type of colour to look for. Nitric is pretty vicous stuff, even jewellers only 'skinny dip' pieces to clean them...

Anything that would bring the green oxide forawrd from the copper content would help to identify it. Also most stainless is at least slightly magnetic - depending on pearlite/austenite structure (conductivity varies too) so a good magnet may help too.

 

Thanks for that confirmation, SukiSolo. I am planning replacing my 316 stainless keel bolts with longer monel units if my lead shoe works out for my build and was concerned the 316 stainless might be subject to contact with salt water at the joint where the shoe is fastened to the fin. We have only a couple of specialized metal suppliers here and I want to be sure I am purchasing monel.

 

If it's small stuff (wire is usually 401), use a loop, if big enough the color is a good giveaway. Monel (400) is a ***** to machine and use 316L if it has to come in contact with steel. Some Monel alloys are slightly magnetic, especially the stuff that's "sulfated" (R-405) for machinability.

 

I haven't cut any Monel lately, but I notice a big difference in the sparks between 316 stainless ans silicon bronze... The bronze made no sparks. it might be worth a test cutting for comparison.

 

Thanks everyone, Good info to jot down in the note book or on the wall of the shop along with a lot of other tid bits of info

 

If you do use Monel, make sure that either the nut or the stud is K-monel (500 series). Monel will gall on itself even using Rotanium Blue Grease.

 

Hey! More useful info, Thanks my good man, ---Geo.