Dear metals/corrosion community,
What is the origin of PREN (pitting resistance equivalent number)? Since PREN is an empirical relationship, who did the original research? Have all of the data, results and conclusions been shared openly?
Thanks!
Nathan
Dear Dr. N.T. Switzner ,
the origins of the PREN have been carefully indicated by Dr. Andreas Heyn .
However, a question arises spontaneously; what is the degree of reliability of this data?
PRENs offer a simple way to compare various alloys and their ability to withstand pitting corrosion.
The British Stainless Steel Association (BSSA) warns,
“The PREN (or PRE) numbers are useful for ranking and comparing the different grades, but cannot be used to predict whether a particular grade will be suitable for a given application, where pitting corrosion may be a hazard.”
While you should always consult an engineer to ensure your materials meet all requirements, we’re going to outline how PRENs are determined and what information this value provides.
For more details, please see the note: What is A Pitting Resistance Equivalent Number (PREN)? - "A look at how pitting resistance equivalent numbers (PREN) are determined and what they do -- and do not -- tell you about a material" – by UNIFIEDALLOYS
Available at: https://www.unifiedalloys.com/blog/pitting-resistance-pren/
Best regards, Pierluigi Traverso
In 1969, Lorenz and Medawar of Thyssen defined a parameter called Pitting Corrosion Resistance Equivalent (PRE) and presented the following relation:
PRE=%×Cr + 3.3 %×Mo + k×%N
Dear Dr. N.T. Switzner ,
the origins of the PREN have been carefully indicated by Dr. Andreas Heyn .
However, a question arises spontaneously; what is the degree of reliability of this data?
PRENs offer a simple way to compare various alloys and their ability to withstand pitting corrosion.
The British Stainless Steel Association (BSSA) warns,
“The PREN (or PRE) numbers are useful for ranking and comparing the different grades, but cannot be used to predict whether a particular grade will be suitable for a given application, where pitting corrosion may be a hazard.”
While you should always consult an engineer to ensure your materials meet all requirements, we’re going to outline how PRENs are determined and what information this value provides.
For more details, please see the note: What is A Pitting Resistance Equivalent Number (PREN)? - "A look at how pitting resistance equivalent numbers (PREN) are determined and what they do -- and do not -- tell you about a material" – by UNIFIEDALLOYS
Available at: https://www.unifiedalloys.com/blog/pitting-resistance-pren/
Best regards, Pierluigi Traverso
Pitting resistance equivalent number (PREN) is such a method and it is widely used as a means of comparing the relative corrosion resistance of different steels. PREN is a theoretical way of comparing the pitting corrosion resistance of stainless steels, based only on their chemical compositions. The early use of the PREN can at least be traced back to the 1960s, since then, a number of empirical formulae for the PREN have been developed and the testing procedure has been specified in the ASTM G48 standard. In general, the higher PREN-value is, the better the corrosion resistance.
The characteristic value PREN only says something about the effect of the alloying elements in their "nominal" concentration. What is not taken into account there is the local distribution of important elements such as Cr and Mo. In many cases, this distribution is significantly below the nominal values in the vicinity of Cr/Mo-rich precipitates and therefore local corrosion is preferred (e.g. pitting, selective corrosion). The properties of the surface (roughness, adsorbates, non-protective layers such as annealing colors) or stress states are also not included in the PREN value. Therefore it can only serve as a rough orientation
Pitting resistance equivalent number (PREN) is a predictive measurement of a stainless steel's resistance to localized pitting corrosion based on its chemical composition. when stainless steels will be exposed to seawater or other high chloride solutions which the pitting corrosion will happen.
Dear N.T. Switzner,
Resource is alloy medication.
PREN resource is chemical composition modification during casting of steel and alloying modification.
Pitting resistance equivalent number (PREN) is a predictive measurement of a stainless steel's resistance to localized pitting corrosion based on its chemical composition. In general: the higher PREN-value, the more resistant is the stainless steel to localized pitting corrosion by chloride. It is a measure of the relative pitting corrosion resistance of stainless steel in a chloride-containing environment. Higher PREN values indicate greater corrosion resistance. The formula for PREN is: PREN = %Cr + 3.3*%Mo + 16*%N.
Ashish
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