What makes a steel stainless?
The addition of chromium and nickel to the iron creates a significant percentage of chromium and nickel atoms at the surface. These atoms form tenacious oxides that seal the surface and prevent oxidation of the iron. The process known as passivation for stainless steel (see the article by Micah Millspaw in a previous issue of BrewingTechniques [1]), is a common means of improving this protective oxide layer through the use of oxidizing acids. Anodizing aluminum alloys is a similar method in that a solid aluminum oxide barrier is created to prevent further corrosion. Like stainless steel, anodized (black) aluminum cookware (Magnalite, Calphalon) is acid neutral and resistant to acidic food because of this heavy oxide layer. Plain (bright) aluminum cookware lacks the degree of surface oxides necessary to prevent reaction with corrosive media. Stainless steel’s Achilles heel: All metals are crystalline materials that have specific crystal structures that are dependent on temperature. Thes
