Titanium for Marine & Seawater Applications

Why seawater service favours titanium

Marine engineers usually arrive at titanium by elimination. Copper-nickel suffers erosion-corrosion at high velocity and is sensitive to sulphide pollution; stainless steels pit and crevice-corrode in chloride; coatings need maintenance and eventually fail at edges and welds.

• Immunity to chloride pitting and crevice attack at ambient temperature. The passive film is stable in oxygenated seawater, including under deposits and in crevices.
• High velocity tolerance. Titanium handles the flow velocities that erode copper alloys, allowing smaller bore and higher heat-transfer rates.
• Ammonia and sulphide tolerance. Polluted harbour water that attacks copper alloys leaves titanium unaffected.
• Weight. Roughly 45% lighter than copper-nickel and well below steel, which matters aboard ship and on topsides.
• Life-cycle cost. Not the cheapest to buy; frequently the cheapest per year of service once retubing and downtime are counted.

Which grade, and when to move off Grade 2

Component map for a marine package

Galvanic corrosion — the question that always comes up

Titanium is noble. Joined electrically to aluminium, zinc or mild steel in a seawater circuit, it drives corrosion of the other metal. Every titanium-to-steel joint on the seawater side needs isolation: insulating gaskets, sleeves around bolt shanks and insulating washers. Titanium itself will be fine; the hull or the steel flange nearby will not be.

The practical approach used in yards: isolate every dissimilar joint, or make both sides titanium.

Repeat orders to European fabricators

A recurring part of our work has been repeat supply of titanium bar and machined parts to a European welding fabricator, ordered against DIN references. The point worth making is not volume but the pattern: repeat orders arrive because the paperwork and the material matched on the first delivery, and the second enquiry therefore did not need re-qualifying.

Classification societies

Shipboard work under a classification society such as DNV or Lloyd's Register typically requires material to be documented and sometimes witnessed. What we do is coordinate documentation: supply material to the ordered standard, provide traceable mill documentation, and support the certification package your project assembles.

Enquiry template

Service:      seawater / ______   operating temp ______ degC
Component:    piping / tube / flange / fastener / plate / ______
Grade:        Grade 2  (or specify ______)
Standard:     ASTM B338 / B265 / B348 / ______ (state revision)
Dimensions:   ______
Quantity:     ______
Fabrication:  straight lengths / cold bends / to drawing (attach file)
Isolation:    insulating gaskets required yes / no
Documents:    MTC / third-party inspection ______ / other ______
Destination:  country ______ / port ______
Required by:  ______

Frequently asked questions