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For a shell and tube marine oil cooler, material selection is critical due to seawater corrosion, fouling, and high mechanical stresses. Below are the recommended materials for different components:

1. Shell (Oil Side)

• Primary Material:
  • Carbon Steel (CS) with corrosion-resistant coating (e.g., epoxy or rubber lining) – Cost-effective but requires maintenance.
  • Stainless Steel (SS 316/316L) – Better corrosion resistance, preferred for harsh marine environments.
  • Duplex Stainless Steel (SAF 2205) – Higher strength and chloride resistance than SS 316.
• Why?
  • The oil side is less corrosive than the water side, but the shell must still resist internal oil degradation and external marine atmosphere.

2. Tubes (Cooling Medium Side – Usually Seawater)

• Best Options:
• Titanium (Grade 2 or Gr. 5) – Best for seawater, immune to chloride corrosion, biofouling-resistant, and long-lasting (used in naval & high-end marine applications).
  • Copper-Nickel Alloys (Cu-Ni 90/10 or 70/30) – Good seawater resistance, anti-fouling properties, and cost-effective compared to titanium.
  • Aluminum Brass (76% Cu, 22% Zn, 2% Al) – Cheaper than Cu-Ni but less durable in polluted seawater.
• Avoid:
  • Stainless Steel (SS 304/316) – Prone to pitting & crevice corrosion in stagnant or chlorinated seawater.
  • Admiralty Brass – Not suitable for polluted or high-velocity seawater.
• 3. Tube Sheets (Holds Tubes in Place)
• Material:
  • Naval Brass (for Cu-Ni tubes) or Titanium-clad Carbon Steel (for Ti tubes).
  • Stainless Steel (SS 316L) with Cathodic Protection – If used, must have zinc anodes.
• Why?
  • Tube sheets face galvanic corrosion due to dissimilar metals (e.g., Cu-Ni tubes + CS shell).
• 4. End Caps / Headers (Water Side)
• Cast Iron (with coating) – Economical but prone to rust.
• Bronze (for Cu-Ni systems) – Corrosion-resistant.
• Stainless Steel (SS 316) – Best for longevity.
• 5. Baffles & Supports
• SS 316 or Coated Carbon Steel – Must resist water turbulence and erosion.
• Key Considerations for Marine Oil Coolers:
• Seawater Velocity: High flow reduces fouling but increases erosion → Titanium is best for high-velocity seawater.
•  Sacrificial Anodes (Zinc) – Needed if dissimilar metals are used (e.g., CS shell + Cu-Ni tubes).
•  Double-Wall Design – Prevents oil-seawater mixing in case of leakage (IMO/SOLAS compliance for some vessels).
• Best Material Combination for Marine Oil Cooler:
• Final Recommendation:
• For maximum durability & low maintenance → Titanium tubes + SS 316L shell.
• For cost-effective solution → Cu-Ni 90/10 tubes + coated CS shell + zinc