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Low temperature black chrome for corrosion resistance in carbon steel

Q. I am working with a firm that uses / processes linear bearing rails made of carbon steel.

I'd like to know more about something a potential vendor called "low-temperature black chrome" plating. Supposedly it has been used for years in semiconductor manufacturing equipment in Japan. Allegedly and as a proprietary plating process it seems to have found an new application in bearing rails as a corrosion resistant plating that goes on very thin adding minimal dimension of .0002" Stainless steel rail is available but it has issues in hardness and cost.

Does this differ from other forms of decorative black chrome? I'd be particularly interested in its resistance to salt spray.

Steve Evers
product development / researcher - Croydon, Pennsylvania
August 12, 2010

RFQ: We import cross roller bearing from Japan that are plated with low temperature black chrome plating or Raydent. We are searching for a domestic source for this process. Can you give us some direction?

Jim Falbe
- Peabody, Massachusetts
October 30, 2017

Ed. note: Sorry, this RFQ is outdated so private contact is no longer available, but public technical replies are still welcome! No public brand/source suggestions please ( huh? why?)

A. Hi. "Low temperature black chrome" and Raydent coatings seem to have very little connection with actual chrome plating.

Although the vendors don't reveal much, those who are offering "low temperature black chrome" seem to be applying an organic, polymer, coating which is infused with chromium-ceramic particles. They do not seem to reveal how they apply it, except "below 0 temperature".

Raydent coating appears to be sort of the same thing applied in reverse order -- a chromium ceramic matrix is deposited on the steel, followed by infusing the cracks and vacancies with a polymer. These are only assumptions gleaned from verbiage which is not intended to inform us how it is done.

Both coatings claim excellent corrosion resistance and good wear resistance for linear bearing and similar applications. Another claimed advantage is that the black color offers contrast with the underlying steel so that wear can be seen. It is obviously difficult to offer a balanced comparison of the performance of secret proprietary coatings to more generic ones, but I think it is not unreasonable to believe that a coating made specifically for linear bearing shafts probably does perform better than the alternatives in that application.


pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
October 2017

October 31, 2017

A. The process has very small build up - only 1-2 microns and has good corrosion resistance. Finished bearing surfaces can be treated with no need for masking or finish machining. There are two companies in Japan that offer this process. They are:
1. Hojitsu; Hojitsu-seiko;
-Have official Raydent® license
-They had bad experience in Korea & Japan, stolen Raydent technology from licensed company. They do not want to export the process from Japan.
2. Mikurodent Co.,;
-Do not have Raydent® license. They call this "Low-temperature Black-chrome plating"

I post this information in an attempt to attract any company that may be able to perform this process in US.

Jim Falbe [returning]
- Peabody, Massachusetts

Steve Evers: What is the name of the "low temperature black chrome" finishing company you were working with? We still cannot find a domestic source of either process.

Isaac Lin [returning]
- Wilmington, Delaware USA
May 30, 2018

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