HXR tubes are commonly made from which materials to resist seawater corrosion?

HXR tubes are commonly made from which materials to resist seawater corrosion?

• A. Stainless steel, nickel alloys, titanium
• B. Copper-nickel
• C. Admiralty copper
• D. Aluminum-brass

Answer: (A)

Seawater is aggressively corrosive because of chlorides, dissolved oxygen, and varying temperatures, so heat-exchanger tubes must resist general corrosion, pitting, crevice corrosion, and stresses. Materials that hold up well in this environment do so by forming very stable, protective oxide films and maintaining strength under seawater conditions. Stainless steel provides a durable chromium-rich passive film and a good balance of strength, weldability, and cost. Nickel-based alloys offer outstanding resistance to chloride-induced corrosion and high-temperature service, maintaining integrity where harsher environments are involved. Titanium develops an extremely stable titanium oxide layer, giving excellent corrosion resistance even in seawater, though it comes with higher material cost and special fabrication considerations. Other options don’t fit as well for tube materials in seawater service: copper-nickel is corrosion resistant in seawater but may not meet all mechanical and high-temperature requirements for HX tubes; Admiralty copper and aluminum-brass are more prone to dezincification and other seawater-related degradation, making them less suitable for long-lived HX tube service.

Seawater is aggressively corrosive because of chlorides, dissolved oxygen, and varying temperatures, so heat-exchanger tubes must resist general corrosion, pitting, crevice corrosion, and stresses. Materials that hold up well in this environment do so by forming very stable, protective oxide films and maintaining strength under seawater conditions. Stainless steel provides a durable chromium-rich passive film and a good balance of strength, weldability, and cost. Nickel-based alloys offer outstanding resistance to chloride-induced corrosion and high-temperature service, maintaining integrity where harsher environments are involved. Titanium develops an extremely stable titanium oxide layer, giving excellent corrosion resistance even in seawater, though it comes with higher material cost and special fabrication considerations.

Other options don’t fit as well for tube materials in seawater service: copper-nickel is corrosion resistant in seawater but may not meet all mechanical and high-temperature requirements for HX tubes; Admiralty copper and aluminum-brass are more prone to dezincification and other seawater-related degradation, making them less suitable for long-lived HX tube service.