It is incorrect to say that DLC does not work to prevent rust.
First of all, TazKristi never said DLC does not prevent rust. That has been repeated a number of times here (I may have even done so), but her actual post does not specify DLC does this:
It might be worth noting, a coating can (and often does) actually make rust/corrosion worse. Water Bug, you are correct, the intended purpose is light discipline.
Second, DLC does
work as a barrier between the steel and any liquid with which it comes into contact. Further, DLC is chemically inert, so the combination of the two does reduce rusting.
Source: http://www.azom.com/article.aspx?Articl ... istance_of
Corrosion resistance is measured by exposure for 24 hours to 10% NaCl solution at 150°F and 15% HCl at room temperature. Figure 6 (a and b) shows optical micrograph of a coated 1020CS sample after exposure to HCl and brine solutions showing that DLC-Si coating provide excellent corrosion protection for the substrate. It is because DLC is chemically inert and acts as a physical barrier between the substrate and corrosion environment provided coating defects are minimized.
and from the conclusions:
Data showed that such a coating provides excellent corrosion protection to internal surfaces of pipes.
The only consideration is the process through which Spyderco applies dlc, as that will affect its amount of provided corrosion resistance.
Of course I'd be interested to hear any actual evidence to the contrary.