Various types of cookers are used in the food processing industry for sterilization of canned food. The basic process involves filling the can with food product, sealing it and heating it to destroy any microorganisms. After the can is heated for the required period of time, it is cooled to ambient temperature either for storage or shipment. During this process, the corrosion of cans and the cooker must be carefully controlled through a properly designed chemical treatment program.

Poor corrosion control was observed in a hydrostatic cooker owned by Princeville Canning, a food processing company located in Princeville, IL. Corrosion rates as high as 54 mpy (1.37 mm per year) were attributed to the aggressive environment and poor quality makeup water. Traditional corrosion inhib-itors and treatment practices were not effective.

Food products continuously canned at the Princeville facility include processed pumpkin and prepared vegetable salads. The hydrostatic cooker at the Princeville facility is a six-pass unit. It has an inner and outer chain for economical running of numerous sizes of metal cans. The unit has an average steam load of 8,000 lb/hr, and the cooling portion of the cooker receives its water from a 30,000 gal cooling canal, which itself is cooled by two small cooling towers.

Aggressive corrosion of cookers is not typical throughout the food processing industry. However, due to some unique characteristics at Prince-ville and the aggressive environment within the hydrostatic cooker, corrosion control became a problem.

Corrosion control can be provided through several treatment programs. At the Princeville facility, the ap-proach was taken to design a program that would specifically address the corrosion of the chain. It was thought that if a persistent film could be developed while the chain was immersed in water, the chain would be protected throughout the other environments.

After two seasons of various treatment program trials, an alternate approach was taken. A quality team was formed, consisting of members of the Princeville staff, a representative from the cooker manufacturer and various BetzDearborn, Horsham, PA, personnel. The objective was to develop an effective treatment program that would protect the cooker, control costs and maximize chain life. Mechanical changes also were made to the treatment program.

The cooperative effort, using a combination of phosphates, nitrite, silica, amine and polymer technology, resulted in the desired corrosion protection of the cooker and its associated equipment. Corrosion rates have re-mained low with an average rate of 1.6 ml (0.04 mm) per year. The reduction in corrosion rates has resulted in dramatic improvements in system operation. It is expected that by maintaining the existing chemical treatment program, replacement of the chains in the cooker will not be required for many years. This corrosion control and monitoring program has since been applied to other locations, where it has found success similar to that seen at Princeville Canning.