CVD Carbides for Corrosion-Resistance Applications

Tie has good resistance to sulfuric acid.l l A passivating oxide layer is formed up to a potential of 1.8 V at which point corrosion becomes severe. TiC is also very resistant to sea water, neutral industrial waste waters, and human sweat. Cr7C3 is even more corrosion resistant and is used extensively as a passivation interlayer. 

Carbides oxidize readily although less rapidly than the nitrides but more so than the borides. Oxidation becomes more rapid going from the Group IV carbides (TiC, ZrC, HfC) to those of Group VI (Cr3C7, MoC, WC). In some cases, a protective film of the metal oxide is formed. Such is the case with SiC, as reviewed in Sec. 5.7 below. 

The carbides are generally not resistant to molten slags and fused salts. Their resistance to molten metal is usually poor. For instance, TiC is attacked by nickel, cobalt, chromium, and silicon. SiC is attacked by aluminum. 

---