In this climate, bicycles require extra cleaning and lubrication. The rusting of painted frames and components such as suspension forks and threaded internal parts can only be prevented by using both internal and external means, since rusting is said to start from inside. If internal components are heavily gresed and have their threads sealed properly, dirt and moisture can not get in. (Also see discussion on overhaul and greaseing)
To prevent external rust, the painted suface must be kept clean and the inevitable paint chips must be dealt with. Model airplane paint and nail polish are common substitutes for the paint your bike has from the factory. Unless you have a black bike, the colored paints rarely match exactly, so a touch up with colored paints will still draw attention to the scratch unless the scratch is widened, feathered, painted with primer and matching color coat and top coated with clear enamel. Therefore it is easier to use clear nail polish to seal the scratches.
Do not buy a clear nail polish with additives such as gelatin (used to strengthen nails?). We want to use a quick drying cheap brand. First clean surfaces to be coated. Dab the stuff onto any scratches and also coat the plalces which are unscratches but which have bumpy surfaces under the paint since there may be thin spots. Water collects in the small indentations between welds, for example. The high spots around welds have the thinnest coating of factory paint.
Paint lightly, allow to dry, then repeat. Examine all surfaces whenever you clean your bike if you are so inclined. Check for cracks at this time, especially around the head tube. Paint rough surfaces a few times each year with clear nail polish and stay ahead of the rust. Some folks make notes about where they need to clear coat, so in the future they won’t miss a spot.
If you don’t do this, we will not criticize you. We know that folks who follow this minute detail may be said to have too much free time. But there are folks out there who will want to know about this.