Stainless Steel
In brewing beer, various types of stainless steel are used. The nonmagnetic 300 series, which includes several types, is commonly used for brewing and fermentation equipment. The more common types for brewing are 304 and 316L stainless steel. They have excellent corrosion resistance properties and are easily weldable. Most brewery equipment is made of Type 304 stainless steel. Type 316L, which has even better corrosion resistance properties, is sometimes used, but it is more expensive. Other 300 series metals should be avoided for brewery use, especially 303.
Chemical Agents
Acid Detergents
– Some acids can be used to clean stainless steel and remove beerstone deposits.
Alkaline Detergents
– Sodium hydroxide, commonly used in CIP systems of commercial breweries, is highly effective at removing organic deposits from stainless surfaces.
Alkaline Disinfectants
– Alkaline disinfectants, such as sodium hypochlorite, do not corrode Type 316 stainless steel.
Passivation
The resistance of stainless steel to corrosion and discoloration is partly due to a passive oxide layer that protects the metal. While this oxide layer forms naturally on clean surfaces exposed to the atmosphere, it can take up to two weeks, which is too long for breweries. Passivation techniques, using acid mixtures containing oxidizing agents, can enhance the formation of the passive oxide layer.
Copper
Copper is generally more resistant to acids than to alkalis. It is usually resistant to non-oxidizing acids such as acetic, hydrochloric, and phosphoric acid, but not resistant to oxidizing acids such as nitric and sulfuric acid, or non-oxidizing acid solutions containing dissolved oxygen.
Aluminum
Caustic cleaners react with aluminum, causing the metal to dissolve and the surface to pit. This reaction can result in a potentially dangerous situation as it produces flammable hydrogen gas.
