-- The Home Page of the Finishing Industry
Serious Education & the most FUN
you can have in metal finishing smiley

No popups, spam, registration or passwords
on this site
current topics
topic 5256



But, I need to get a good finish (bright and smooth black or blue black). In order to get this good finish, I'm thinking of two possibilities:

1-The best alternative is that perhaps some additive can be added into the molten salt bath, in order to get the finish I am looking.

2-If it is not possible to get the adequate finish with this, I'm think in l add one more process, for black oxidising the nails. I know that this can be achieve with hot alkaline baths of NaOH, but I'm new in this, and don't know much about this. Somebody can help me with some information about this( explanation about the process, or a right formulation, like temp., time, composition of the bath)

Thanks a lot in advance.



Victor -

To achieve a smooth & shiny black finish, you must first start out with a smooth & shiny part. Black oxide is a conversion coating and WILL NOT cover up any cosmetic blemishes. By the same token, it will leave a part as shiny as it started without changing any dimensions. As far as any additives, that won't help and in fact may hurt the formation of the black oxide.

The general parameters are to run the bath at 285 degrees F, and to have the parts in the tank for 5-20 minutes. If you use a powdered product, you'll probably be adding 5.5 - 6 pounds of salt per gallon of water.

Dan Brewer
chemical process supplier - Gurnee, Illinois


The blacking bath consists of mainly NaOH plus NaNO3 and NaNO2 boiling at 140 deg C. Occasional addition of extra nitrite gives better colour. If you use an alkaline deruster as the preclean stage (100 g/l NaOH + Sodium gluconate and/or triethanolamine) you will get greater tolerance to blacking bath changes.

Roger Bridger
- Croydon, UK

If you have a question in mind which seems off topic, please Search the Site

ADD a Comment to THIS thread START a NEW threadView CURRENT TOPICS

Disclaimer: It's not possible to 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 may be deliberately harmful.

  If you need a product/service, please check these Directories:

JobshopsCapital Equip. & Install'nChemicals & Consumables Consult'g, Train'g, SoftwareEnvironmental ComplianceTesting Svcs. & Devices

©1995-2018, Inc., Pine Beach, NJ   -   About   -  Privacy Policy
How Google uses data when you visit this site.