Metal finishing Q&As since 1989

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What is Porous Chrome?

My question is, what is porous chrome, and what is the process as to the application? I have a friend in Cairo Egypt that has asked me the question. He is bidding on a job that requires that a cylinder, for lubrication characteristics, have a final chrome plated porous surface. Desired thickness to be between .002-.008 of an inch.

Thanks in advance,

Charles H. Collins
Plating Shop - Watervliet, New York, USA
2004

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That is an interesting issue, Mr. Collins, because I'm not sure that there is really a universally accepted definition of porous chromium. But an old version (1987) of AESF's "Hard Chromium Plating" illustrated lecture by Logozzo and Schwartz asserts the following definition: "Porous chromium is the term given to chromium deposits whose surfaces have been modified to retain oil". You might still be able to still get this document from AESF.

For a current but brief treatment of the subject, see ASM Metal Handbook, Vol. 5, "Surface Engineering".

But get Mil spec C-20218 at http://assist1.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=14159 because it involves quite a bit of detail in terms of plating, post-plating etching, and machining.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004