Corrosion - one of the main challenges

• The focus of current standards and guidelines on lifetimes of less than 15 years
• Learnings from the offshore oil and gas industry not being implemented
• Failing systems repeatedly used
• Problems not occurring directly but after 2-10 years
• Insufficient corrosion and material know-how as part of the design/project
• The operator not being the designer, but having to deal with long-term problems

Material needs in marine environments

A parameter for comparing the resistance to pitting in chloride environments is the PRE number (Pitting Resistance Equivalent). The PRE is defined as, in weight-%: PRE = %Cr + 3.3 x %Mo + 16 x %N

For marine applications PRE > 40 is recommended and the following diagram compares the PRE and yield strength for a number of currently used grades.

Risks in offshore environments

Splash zone

• Alternating wet and dry
• The most critical zone
• High chloride content can be formed on the surface

Seaspray

• Chloride deposits
• Pitting corrosion

Clamps and deposits

• Tight spaces
• Crevice corrosion

Immersed

• Pitting or crevice corrosion

Biofouling

• Introduces crevices (and corrosion potential)
• Adds weight
• Increases friction

Read more about our duplex stainless steels