No cost, no registration, no passwords -- just aloha, fun & authoritative answers
(as an eBay Partner & Amazon Affiliate we earn from qualifying purchases)

Where the
world gathers for metal finishing
Q&As since 1989

-----

Problems in Blackodising

Q. WE ARE DOING BLACKODISE TO MS/EN 8 PARTS AS UNDER:
1] 5 KG SODIUM NITRITE + 10 KG caustic soda [affil links] + 10 LTR WATER
2] BOILING WITH GAS HEATING
3] ACID CLEANED COMPONENT PUT INTO HOT MIXTURE FOR 5-10 MINUTES

BUT WE ARE FACING PROBLEMS AS UNDER:
1] WE DO NOT KNOW THE STEP TO STEP PROCESS LIKE MIXTURE / TEMP / TIME
2] SOMETIMES WE GET IT RED, SOMETIMES NO BLACK, SOMETIMES POOR BLACK
3] HOW MANY KGS CAN WE DO FROM 5 KG OF MIXTURE?
4] HOW CAN WE IDENTIFY THAT NOW WE HAVE TO REPLACE THE MIXTURE?
5] INSTRUMENTS TO IMPROVE STRON BLACK + SHINING
6] WE HEARD ABOUT SEVEN TANK PROCESS? WHAT IS IT
7] BEST OPTION? CAN COLD BLACKODISE GIVE US SAME / BETTER SHINE?
8] ANY CHEMICAL ADD-ON WHICH CAN IMPROVE THE BLACKODISE ?

MANISH BAVISHI
MANUFACTURER - AHMEDABAD, GUJARAT, India
October 14, 2008

A. UNDERSTANDING BOTH METHODS
A summary of the hot and cold blacking methods.

1. Hot blacking converts the metal surface into an iron oxide, which has no oil absorption properties. It is a glossy finish and has a black appearance when dried without oil.

2. Room Temprature blacking converts the metal surface to a copper complex, which has excellent oil absorption properties. It is a matte finish and has a dark grey appearance when dried without an oil. The oil is an important component of the process because it helps to retain the black colour and provide protection against oxidation.

ULHAS DUNDAGE
- Pune, MAHARASHTRA, India
May 13, 2013

A. Thanks Ulhas.

Manish may also wish to review our FAQ "Black Oxide and Cold Blackening". In the USA (where this site is based) we use the term "black oxide" rather than "blackodising"; if people search the site for "black oxide" they will find dozens of threads addressing Manish's issues.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 13, 2013

Functions of Sodium Nitrate & Caustic Soda in Blackodising / Blackening Process

Q. Can any one guide what are the Functions of Sodium Nitrite Sodium Nitrate and caustic soda [affil links] in Blackodising / Blackening Process?

Chintan Mehta
Partner - Bhavnagar, Gujarat, India
December 6, 2013

adv.
this text gets replaced with bannerText

(No "dead threads" here! If this page isn't currently on the Hotline your Q, A, or Comment will restore it)

Q, A, or Comment on THIS thread -or- Start a NEW Thread

Disclaimer: It's not possible to fully diagnose a finishing problem or the hazards of an operation via these pages. All information presented is for general reference and does not represent a professional opinion nor the policy of an author's employer. The internet is largely anonymous & unvetted; some names may be fictitious and some recommendations might be harmful.

If you are seeking a product or service related to metal finishing, please check these Directories: