Aqueous Solutions Corrosion Resistance Ladder – Stainless Steels and Nickel Alloys
A ranking of the relative corrosion resistances of stainless steels, specialty stainless steels and nickel alloys is provided. The ranking of each stainless steel or alloy is made by calculating their individual PREN values. The PREN formula is from NACE MR0175/ISO 15156 sour service standard. The PREN is a relative ranking of the stainless steel or alloy to its resistance to pitting corrosion in aqueous solutions with chlorides and oxygen. For example, for those steels and alloys with PREN of 40 or higher, they are corrosion resistant to seawater.
Note although this ladder is a convenient means of comparing corrosion resistance of various stainless steel and nickel alloys, the ranking is GENERAL, please review specific corrosion data for each steel or alloy to determine their exact corrosion rates in the fluid(s) considered. For example, most of the “superalloys” in the ladder have specific “Achilles Heels”: solutions that will aggressively corrode them.