big swooper, page-20

uses of molybedenum J

Molybdenum containing stainless steels are used in a wide variety of demanding applications where molybdenum-free stainless steels cannot provide sufficient corrosion protection. Typical industries are:

Chemical process
Power
Food and beverage processing
Water and wastewater handling
Architecture, building and construction
By far the most widely used molybdenum containing stainless steel is Type 316 which contains 2% molybdenum. Its varieties (316, 316L, 316H, etc.) claim around ten percent of the total stainless steel market. They provide greatly improved corrosion resistance compared to the workhorse austenitic Type 304 and its varieties which represent about sixty percent of the total stainless steel market. Type 316 is therefore usually the next step up if Type 304 does not provide enough corrosion resistance. Type 316 is often considered the standard material for chemical process equipment.

Type 316 stainless steel is used for outdoor architectural applications near the ocean, in areas where roadsalts are used, and in environments with significant urban or industrial pollution. Many of the most prestigeous buildings in the world, such as the Jin Mao in Shanghai, or the Petrons Towers in Kuala Lumpur use molybdenum containing stainless steel in their facades to provide a long, low maintenance, service life.

However, if the conditions are more aggressive a higher grade of stainless steel such as 317L, 317LMN, 904L, duplex 2205 or a 6% molybdenum containing stainless steel should be selected. The correct stainless steel grade for a given application depends on many parameters such as chemical composition of the environment, temperature, pH, etc. The lowest cost grade that is resistant to corrosion in a certain environment should be chosen for the most cost effective solution.

Examples of more aggressive conditions include chloride containing solutions at elevated temperature for example in food processing or flue gas desulphurisation. Solutions with high chloride content, for example sea water, are also aggressive and require stainless steel with a higher molybdenum content.

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Zinc