AFCO 2558 Shield-CA is an environmentally-friendly citric acid based product designed for the passivation of stainless steel equipment. Since AFCO 2558 Shield-CA contains citric acid and does not contain any nitric acid or 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.