In general: the higher PREN-value, the more resistant is the stainless steel to localized pitting corrosion by chloride.
In some instances stainless steels with PREN-values > 32 may provide useful resistance to pitting corrosion in seawater, but is dependent on optimal conditions.
[1][2][3] These alloys need to be manufactured and heat treated correctly to be seawater corrosion resistant to the expected level.
The value should be calculated for each heat to ensure compliance with minimum requirements, this is due to chemistry variation within the specified composition limits.
They commonly range from: to: There are a few stainless steels which add tungsten (W), for those the following formula is used: All % values of elements must be expressed by mass, or weight (wt.