Years ago Ideale in France made some beautiful saddles with aluminum rails. They weren't the standard 1/4" (or so) rails used today, but rectangular beams about 1/2" tall x1/8" wide. I never hear of a failure on these, but they were killed off by integrated posts a la Campagnolo which firmly established the standards for rails we still use today.

Whether painted or chromed, solid or tubular steel rails will hold up fine as long as water can't wick along the cradle and deposit corrosive salts.