Which material is least suitable for HXR tubes in seawater service?

Which material is least suitable for HXR tubes in seawater service?

• A. Carbon steel
• B. Stainless steel
• C. Nickel alloys
• D. Titanium

Answer: (A)

In seawater service, the material for heat exchanger tubes must resist corrosion from chloride-containing water over long periods. Carbon steel lacks a durable, protective oxide in this aggressive environment, so it corrodes quickly, developing uniform rust, pitting, and crevice corrosion, especially at the higher temperatures and pressures found in heat exchangers. This rapid degradation can lead to leaks and reduced performance, making carbon steel the least suitable choice. Stainless steels form a chromium-rich passive layer that provides good resistance in seawater, though some grades can still be susceptible to localized attack under certain conditions. Nickel alloys and titanium rise even higher in corrosion resistance, with titanium forming a very stable oxide that stands up well to seawater; nickel alloys offer excellent corrosion resistance across a wide range of seawater conditions, though they are more costly.

In seawater service, the material for heat exchanger tubes must resist corrosion from chloride-containing water over long periods. Carbon steel lacks a durable, protective oxide in this aggressive environment, so it corrodes quickly, developing uniform rust, pitting, and crevice corrosion, especially at the higher temperatures and pressures found in heat exchangers. This rapid degradation can lead to leaks and reduced performance, making carbon steel the least suitable choice.

Stainless steels form a chromium-rich passive layer that provides good resistance in seawater, though some grades can still be susceptible to localized attack under certain conditions. Nickel alloys and titanium rise even higher in corrosion resistance, with titanium forming a very stable oxide that stands up well to seawater; nickel alloys offer excellent corrosion resistance across a wide range of seawater conditions, though they are more costly.