PREN stands for Pitting Resistance Equivalent Number, and it’s vital for calculating how well stainless steel and other alloy materials withstand corrosion, specifically pitting corrosion. This condition causes small holes that can lead to less durability and it can be challenging to detect.
The PREN number formula computes the percentages of specific properties in a piece of material, making it useful to compare the resistance of two or more samples. For accuracy, the comparison materials must belong to the same alloy family — duplex, ferritic or austenitic.
To calculate PREN, manufacturers examine the amounts of several chemical elements within the alloy — Chromium, Molybdenum, Tungsten and Nitrogen. The higher the result, the more pitting corrosion resistance the material has.
Corrosion Resistant Alloys provides this free PREN calculator for reference — simply enter your elemental values to get started.