Why this matters
Titanium pipe and fittings dominate seawater heat exchangers, ballast piping, hypochlorite handling and many chloride-rich chemical services because titanium is essentially immune to chloride pitting and stress corrosion cracking. The two grades that account for most commercial piping volume are Grade 2 (commercially pure titanium) and Grade 12 (Ti-0.3Mo-0.8Ni). They are routinely covered by ASTM B338 / B363 (pipe and fittings) and ASME SB-338 / SB-363, and are recognised in ASME B31.3 for pressure piping design.
Key technical facts
Titanium Grade 2 (UNS R50400) is unalloyed titanium with controlled iron and oxygen for moderate strength. It offers excellent resistance to oxidising and mildly reducing environments and is the workhorse for seawater service. It is essentially immune to stress corrosion cracking in seawater and resists pitting in hot chloride solutions.
Titanium Grade 12 (UNS R53400, Ti-0.3Mo-0.8Ni) is a near-alpha alloy designed to extend titanium's corrosion envelope into mildly reducing acids and elevated-temperature chloride service. It typically retains adequate strength up to higher temperatures than Grade 2.
Key design notes:
- ASME B31.3 lists allowable stresses for both grades; design wall thickness is typically a fraction of an equivalent carbon steel design due to titanium's corrosion margin.
- Both grades are immune to chloride stress corrosion cracking in normal seawater.
- Galvanic compatibility: titanium is noble; couple to suitable materials or use isolation.
