Eight-year exposure tests of six stainless steels to underwater and atmospheric environments in Panama Canal Zone are described. Test environments included sea water immersion, lake water immersion, seashore inland, inland, sea water mean tide, and seashore. Structural steels, phosphor bronze and naval brass were also evaluated for comparison. Stainless steel plates later were galvanically coupled to carbon steel strips for testing in tropical waters. Stainless steels were not recommended for sea water service where perforation of structure is a consideration. They gave excellent results, however, in tropical fresh water. Tropical atmospheres appeared more corrosive to stainless steels than did temperate climates. 4.2.7, 6.2.5