Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Blackodising of metal surface
January 17, 2011
Dear All
We are facing regular problems in blackodising of M.S. parts Some time they are z black but majority times parts are brown or some what rusty.
Can any one inform what is correct procedure of blackodising?
What type of chemicals used to get the black surface finish & is there any one who sell it?
buyer of M.S. components - Belgaum Karnataka India
January 17, 2011
Hi, Nitin.
Yes, many companies supply black oxiding chemistry. It is distributed both by plating process distributors and by the gunsmithing industry. You haven't given us any information about what you are doing that would help anyone figure out why your parts come out brown or rusty instead of black.
The Metal Finishing Guidebook offers an introduction to the subject, and includes this formulation:
caustic soda ⇦liquid caustic soda in bulk on
Amazon [affil link]
80 oz/gal
Potassium nitrite 30 oz/gal
Potassium nitrite 20 oz/gal.
Remember that these very hot solutions (295° F) are very dangerous due to their propensity to "erupt" if the necessary evaporation losses are not made good properly but allow pure water (boiling point 212° F) to find itself in the body of the solution and suddenly flashing to steam.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Parts rusting is almost always linked to an improper balance of water to salts. 99% of the time it's not enough water. The salts should be at a rolling boil with the temperature starting at 280 F and going up to 300 F as the water boils off. After the solution hits 300 F the parts must be removed and the salts taken back down to 280 F by adding water.
Rod Henrickson
gunsmith - Edmonton, Alberta, Canada
January 28, 2011
January 4, 2012
We have just started BLACKODISING of MS,N8,N31,N24 materials.
(studs,Fixtures,nuts,packing plates)
We are facing following problems.
1.coating is uneven.
2.surface dose not shine.
3.it look brownish.
We use following mixtures
caustic soda ⇦liquid caustic soda in bulk on
Amazon [affil link]
sodium cyanide
water
Please help us to make it right.
- Pune, India
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