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Best substrate for Ti-Gold PVD coating

I want to make some outdoor handrails and window cladding with a mirror finish Ti-gold PVD coating. I have had some samples made that were PVD coated on 304 stainless steel. The problem is that the surface scratches. I was told that it scratches because the stainless is relatively soft compared to the very thin but very hard TiN coating. The stainless apparently deforms under the coating. What would be the best base metal and plating material(s)to use to make a fairly scratch resistant, mirror surface that could be PVD coated? I am looking for a 25 year life span. The PVD coating is being done in China because I could not find a domestic company that can PVD coat parts this long. Some pieces would be tubing 2.5" OD X 13' long. Others would be angles bent from 0.040" long thick material up to 13' long. Any help you could give would be greatly appreciated.

Dwight Landis
custom home builder - Malibu, California
April 11, 2009

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There are two regimes of TiN coating. One is for parts that are subject to wear, the other that are coated for decorative purposes only. The latter coatings are very thin, deposited primarily on chrome/nickel plated materials at low temperature (~150 C). The former are thick, deposited on bare metal and carbide, at very high temperature (~450 C). It is possible that they are giving you a decorative, hence very thin coating with no scratch resistance. This fits with the size of the parts. 13 feet is extremely long for hard PVD coatings. It seems that you have two choices: 1) Segment the rails into 2' lengths; or, 2) have electroless nickel and hard chrome deposited on the rails before the TiN.

Jim Treglio - scwineryreview.com
PVD Consultant & Wine Lover
San Diego, California
April 17, 2009