Titanium and its alloys exhibit excellent general corrosion resistance, but they may still be susceptible to certain types of localized corrosion under specific conditions. The main forms include:
1. Crevice Corrosion
Occurs in narrow gaps (e.g., under gaskets, bolts, or deposits) where oxygen diffusion is restricted.
More likely in high-temperature chloride environments (e.g., seawater, chemical processing).
Prevention: Optimize design to avoid stagnant zones, use higher-grade alloys (e.g., Ti-0.2Pd, Ti-6Al-4V ELI).
2. Pitting Corrosion
Rare in pure titanium but possible in highly oxidizing acidic/chloride media (e.g., hot concentrated chlorides, bromides).
Alloying elements (e.g., Mo, Ni) can improve resistance.
3. Galvanic Corrosion
When titanium contacts less noble metals (e.g., steel, aluminum) in conductive electrolytes, accelerating the partner metal's corrosion.
Mitigation: Insulate dissimilar metals or use compatible materials.
4. Stress Corrosion Cracking (SCC)
Requires combined tensile stress and aggressive environments (e.g., hot salts, methanol/halides).
Titanium alloys are generally resistant but susceptible in specific conditions (e.g., Ti-8Al-1Mo-1V in NaCl).
5. Hydrogen Embrittlement
Hydrogen absorption (e.g., from cathodic protection, pickling, or high-temperature service) can cause brittle failure.
Controlled by limiting hydrogen exposure and using low-interstitial alloys (e.g., ELI grades).
Conclusion: While titanium resists most corrosive environments, proper material selection (e.g., alloy grade, surface treatment) and design (e.g., avoiding crevices) are critical to prevent localized corrosion in demanding applications.
