Selection of Corrosion-Resistance Alloys

Alloy selection, from a corrosion standpoint, can be considered to be a three-step process. First, resistance to general corrosion must be ensured, which is primarily a function of the chromium content 

The limits given assume complete oxygen free environments. 

If one of the listed parameters exceeds the given limit, the need fortestingofthe material according to ISO 15155-3 should be evaluated. 

The temperature limit may be increased based upon evaluation of specific field data and previous 

The close correlation between pitting resistance and resistance to anodic cracking should be noted. This apparently results from the ease of crack initiation under the low-pH-high-chloride conditions found in pits. Therefore, higher molybdenum can also increase resistance to anodic cracking. 

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Proper selection of corrosion-resistant alloys and proper welding procedures to avoid corrosion and cracking-related failures will assist Coatings and cathodic protection help corrosion control... 

The selection of corrosion-resistant alloys for service in multi-oxidant atmospheres of high Pq is based primarily on oxidation resistance and, specifically, on the tendency of the alloy to form a Cr203-, Si02-, or Al203-rich scale. Although this is true for I0W-P02 atmospheres also, as will be discussed in the following sections, the base-metal and specific alloying elements play... 

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