Shield CA (AFCO 2558) is an environmentally friendly citric acid-based product designed for the passivation of stainless steel equipment. Since AFCO 2558 contains citric acid and does not contain any nitric acid nor other mineral acids, it does not pose the environmental, safety, and health hazards that are present when using nitric acid-based products for passivating. In addition, citric acid has been found to be much more effective for passivation than nitric acid.