I guess I don't understand how an aluminum bike in your garage is going to keep the steel bike in your garage from rusting.

I do get a little rust on my old custom steel frames if I suffer a paint chip, but I have them repainted from time to time, so no big deal. I have had to have an aluminum frame replaced under warranty due to corrosion at the bottom bracket from sweat. Go figure.

Are you suggesting that cleaning the steel bike will help prevent rust, which it will by the way? Or are you suggesting you have to be careful when cleaning a steel bike not to induce rust? Not sure what you mean. In any case I keep my steel frames clean with Windex and paper towels used frequently. Dust and dirt contribute to corrosion by damaging the paint. I never use running water on the steel bike (never a hose).