Custom 455 stainless resists staining in normal air atmospheres, and shows no corrosion in fresh water. Test in 5% salt spray at 95 °F(35 °C) and in 5% ferric chloride at room temperature have demonstrated good resistance to pitting and rusting. Laboratory test s in a variety of mild chemical environments have shown that the level of general corrosion resistance is superior to that of the 12% chromium steels (Type 430). In most tests there was no significant effect of aging temperature on corrosion resistance. Hydrogen embrittlement tests in 5% acetic acid saturated with sulfuric hydrogen at room temperature show the same degree of susceptibility as other high-strength martensitic stainless steels. All high-strength steels are subject to stress corrosion under certain stress conditions and in certain environments. Numerous severe tests have been conducted to evaluate the behavior of Custom 455 stainless in different environments, and to determine the effect of aging temperature on resistance to stress -corrosion cracking. These tests include U-bend specimens, direct tension specimens, C-rings and pre-cracked cantilever beam specimens. Environments have included marine atmospheres, 20% salt spray, and 3-1/2% sodium chloride solutions. All tests have shown that Custom 455 stainless has inherently good resistance to stress-corrosion cracking, and that this resistance improves markedly as aging temperature is increased. For optimum corrosion resistance, surfaces must be free of scale and foreign particles and finished parts should be passivated.