unknown coating question (unknown to me)

[baca262]

hello everyone, this is my first post on this forum.

i've been wondering about this one specific coating that i haven't been able to google and find details about. it is used as a low friction, high wear resistance and anti stick coating in bicycle suspension fork stanchions and shock shafts.

here's an image of one of the forks that uses it:
(link dead)

this upper half of BOXXER inscribed on the stanchion tube looks very similar to DLC to the naked eye, but i don't think it's DLC. my question is about this yellowish-gold coat that is on the rest of the tube, it seems to be about 0.2-0.1mm thick and tends to flake off in tiny flakes when badly scratched or nicked, it doesn't appear amorphous like DLC when broken off but i have no clue what is it. it is usually erroneously referred to as some sort of anodization or TiN but i don't think it's either since TiN looks like polished gold and anodization would have poor friction and wear properties. in person it's of a pale golden colour and appears somewhat fuzzy.

so, i need an opinion of someone educated on the topic to what kind of coating is it.

the tubes it is applied to are 7000 series aluminum and they slide on oil lubricated bronze/steel teflon-coated bushings.

EDIT: excuse my english, it isn't my native language... :-S

[wilfred1963]

(link dead) try this link or cut and paste might be of some help for you

[durkie]

i've always been under the impression that it is titanium nitride. i believe they can control the color via ti/n ratio. see also this: http://www.vaportech.com/pdf/VaporTech_RockShox.pdf

[baca262]

thank you for the replies. nice find durkie, the forks in the pdf are early 2000 era, but it says the standard production forks have anodized tubes, so i was wrong, it is some form of hard anodization that i know squat about.

this rules out tin coating as standard production coating, so, now my question is about hard anodization techniques that achieve relatively low friction and high wear resistance

[djewell]

The old production method was anodization. The point of the article was that TiN was a good replacement for anodization. It provided lower friction, yet acceptable wear resistance.

[baca262]

no, they kept the old finish for standard production models (tin coat is much more expensive), this may have been used only in their racing department. they are experimenting with dlc these days, dlc may go into standard production in a year or two.

anyways i think i finally managed to find out what is the standard finish - it's type III hard anodization which yields this fuzzy golden color on 7075 alloy according to this - http://www.finishing.com/406/33.shtml

thanks for the help everybody