Black oxide process

[Shade Tree Welder]

CAUTION: BLACK OXIDE PROCESS IS DANGEROUS!

IF YOU DON'T KNOW HOW TO HANDLE THESE CHEMICALS SAFELY,
PLEASE DON'T DO THIS PROCESS!

Base formula (grams)
Water ....... 1000 g (1 liter) Distilled, do not use tap or softened water.
NaOH ......... 600 g (Sodium Hydroxide)
NaNO2 ......... 25 g (Sodium Nitrite)
Total ........ 1625 g

• This solution will boil at around 280°F.
• You have to have it at boiling before you put parts in it.
• It is very alkaline and very hot so be very careful.
• You can get caustic burns from it very fast, so be very careful.
• Heavy rubber gloves, a rubber apron and a face shield are recommended.
• It is best if you do this outside in an open environment.

The pot you use has to be stainless steel; also anything that goes in the pot
has to be steel or stainless steel. Any aluminum or zinc will kill the bath and
brass and copper are not good for it either. 304 stainless aka 18-8 stainless
steel is just fine that is what I used. 316 is better but you likely will only see
the difference in your wallet.

I have a pot that holds about 5 gallons. I mixed up a little over 3 gallons of
solution, if you cannot covert well. Here is my 3 gallon mix.

Component ... Amount
Water ........... 3.0 gallons
NaOH .......... 15.0 pounds
NaNO2 ........ 10.0 ounces

You can buy the Sodium Hydroxide and Sodium Nitrite on amazon.

If you are doing a number of batches the water will boil off. You can add
more water, but be VERY CAREFUL. The bath is going to be >280°F. Water
boils at 212°F, so add cold water slowly you will hear it boiling as you are
adding it. If you add it too fast or add warm or hot water you could have it
flash to steam and end up wearing most of your very hot very caustic bath
and be heading to the ER and ICU for steam and chemical burns.

Submerge the parts you want black oxided until the color you want is achieved
you will need basket for smaller parts and you can use iron or stainless wire
to attach to larger parts. You might need to move the wire to get complete
coverage.

Also have 2 or more buckets of cold water handy for rinsing and cooling off parts.
Rinse the parts in the buckets and keep the same order. The first bucket will get
a bit alkaline after doing several batches.

BE VERY CAREFUL doing this!!!