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How to achieve Brown Zinc Chromate finish?


A discussion started in 2012 and continuing through 2017 . . .

August 14, 2012

Q. Hello Again. Here is another item looking for help. How to achieve or purchase dichromate crystals of a brown color, not a reddish brown more like a root beer color. If need be, who does this.

This color is also a highly desirable finish used on Chrysler muscle car parts form 65 to 73. No one can seem to produce this finish.

Bill Meerholz
- Pompton Plains, New Jersey


August 17, 2012

A. Hi, Bill. Readers might not understand a verbal description. Please try to send pics if you can. Thanks!

Ted Mooney, finishing.com
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


November 10, 2014

Q. Attached are some pictures of 2 different Chrysler original new never used or subjected to sun or bright lighting.

58797-1a brown chromate  58797-1b brown chromate  58797-1c brown chromate 

Base is definitely zinc or cad. Probably zinc. On the backside of the bigger catch you will see a spot where I applied few drops of 50% Muriatic acid & water. Took approx. 10-15 seconds to get to bare metal. The brown chromate does not scratch easily, as blacks do.

Can anyone shed any light on this question?

Bill Meerholz [returning]
- Pompton Plains, New Jersey



What is brown zinc that was used on Chrysler parts late 60's-early 70's.

October 23, 2016

Q. What is brown zinc that was used on Chrysler parts late 60's early 70's. Hood latches, etc.

Bill Meerholz [returning]
Restore many original Chrysler parts including hood latches that are the brown zinc finish. - Pompton Plains, New Jersey


January 8, 2017

Q. Can someone please advise something about this what is believed to be brown chromate or what it is or how to achieve it? What is the finish on latches pictured?

Bill Meerholz [returning]
- Pompton Plains, New Jersey


58797

Electrolytic and Chemical Conversion Coatings

January 2017

A. Hi Bill. Nobody has related their experience with this finish in 4-1/2 years now. There are two ways to get varied colors in chromating: dyeing the chromate or changing the operating conditions. The attached page from Biestek & Weber =>
implies that brown chromating can be accomplished, without dyeing, by adjusting the sulphate ratio. I'm not sure how much practical help that will provide though :-(

Regards,

pic of Ted Mooney
Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey


January 24, 2017

The dark chromate conversion coating described and seen in the photos is one of two possibilities: (1) an olive drab chromate, or (2) a dark yellow chromate. In the more common yellow (or gold) chromates, if an article is (a) left in the chromate for a longer period of time, or (b) the chromate is too concentrated, or (c) the pH is low, then the chromate will be dark, running towards brown. If the chromate is too dark, the chromate conversion coating will be friable and powdery, so these processing conditions are wisely avoided.

tom_rochester
Tom Rochester
Plating Systems & Technologies, Inc.  

Jackson, Michigan, USA


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