THE Materials Oracle
Join Date: Feb 2006
Location: Finally... home :-)
Bikes: Univega Alpina 5.1 that became a 5.9, that became a road bike... DMR TrailStar custom build
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Parkerising isn't much more durable, it's a thin layer of manganese phosphate laid down from an autocatalytic acid process, so you have to be careful with it on high-strength steels. The aerospace community mandates post-treatment bakes for anything over about 1000MPa UTS with any form of acid-bath treatment, for good reason.
And even then, it's not particularly anticorrosive. You have to oil the rough surface, and keep re-oiling it if it's not to be used in an anhydrous environment, y'know, like, the world outside.
Titanium nitride is fine for decorative coatings and such, but it's rather brittle and prone to spalling if the substrate is too ductile and tough, like, for example, a bike frame. It goes onto HSS tools because they're treated to over 60 Rockwell C and full of massive carbides, which make them break before they deform, thus ensuring the brittle coating has a substrate that behaves the same. A number of manufacturers have moved from titanium nitride to titanium aluminium nitride, which is a pleasing dark blue colour and much more forgiving.
Goltec used to throw down TiN on anything they sold, but that was things like hub bodies, casettes etc. I have no anecdotal evidence on how long it lasted on them, I'm afraid.
Oh, and it's not particularly sacrificial as a coating.