Stainless steels are common in the food and beverage industry for manufacture, bulk storage and transportation, preparation and presentation applications. Depending on the grade of stainless steel selected, they are suitable for most classes of food and beverage products. The 316 and 304 grades are often referred to as the food grade stainless steel. There is no known official classification for this and so, depending on the application, the equally common 1.4301 and 1.4016 grades may be suitable for food processing and handling.
Most containers, pipework and food contact equipment is manufactured from either 304 or 316 type austenitic stainless steels. The 17% chromium ferritic stainless steel (430 type) is often used for splashbacks, housings and equipment enclosures, where corrosion resistance requirements are not so demanding. In addition to these non-hardenable austenitic and ferritic types higher strength ‘duplex’ types, such as grades 1.4362 and 1.4462 are useful for ‘warm’ conditions (i.e. over 122°F) where stress corrosion cracking be a risk, such as in brewery sparge tanks. Hardenable “martensitic” type stainless steels are widely used for cutting & grinding applications, especially where knives are needed.
If the grade of stainless steel is correctly specified for the application, corrosion should not be encountered. The types of corrosion to which stainless steels can be susceptible can be useful in identifying problems due to wrong grade selection or inappropriate use of equipment.
Effective cleaning is essential in maintaining the integrity of the process and in prevention of corrosion and maximizing safety in the food processing industry. The cleaning method selected and the frequency of its application depends on the nature of the process, the food being processed, the deposits formed, hygiene requirements etc. The cleaning methods suitable for stainless steel equipment are:
Chemical disinfectants are often more corrosive than cleaning agents and care must be exercised in their use.
Operation equipment often contains gaskets or other components that can absorb or retain fluids. These liquids may be become concentrated by evaporation and corrosion may develop as a result. Equipment should be disassembled occasionally for thorough cleaning to prevent corrosion and unsanitary conditions from emerging. If the disassembled equipment exhibits corrosion (crevice corrosion usually), then the corroded surfaces should be cleaned and a maintenance schedule with should be written up and observed frequently.