Will using a non stainless steel, ruler to measure my volumes have an effect on the beer? Will there be leaching or off flavors created? The ones I'm looking at are "hardened steel".
Steel will rust quckly and should be avoided. I use to have a copper stip hanging inside my kettle that I marked with lines every half gallon. I never had any problem with off flavors or corrosion. It did darken some during storage and brighten during the boil so some material was dissovling into the wort but all copper parts in a brew system do that.