Road salt does not rust your car in one winter. It rusts it over five, quietly, from the inside of the rocker panels out. By the time you see bubbles in the paint, the metal behind them is already gone.

The good news is that salt needs three things to do damage: metal, moisture, and warmth. Take away any one of them for long enough and you slow the whole process to a crawl.

Wash the right way, at the right time

The most important thing is when you wash. Do it after the roads dry, not during a snow storm or right after a plow passes. Washing while the roads are still wet with brine just puts fresh salt back on the car before you get home.

Watch the forecast and pick a day when it stays above freezing for a few hours. That is your window.

Get the underside

1. Spend the extra few dollars on the undercarriage wash. This is the only part of the car that actually matters for rust, and it is exactly the part a regular wash misses.
2. Wash the wheel wells and the inside of the doors. Salt collects in the seams at the bottom of doors and around the wheel arches.
3. Open the doors and the trunk and wipe the rubber seals after the wash. Grit in the seals tears them over time.
4. Hose out the floor mats separately. Salt crystals dry into the carpet and keep working every time someone steps in with wet boots.

Do not skip the wheel wells because they look clean. The liner hides a shelf of salt sitting directly against metal.

Things that cost little and help a lot

• Mud flaps keep spray off the lower panels where rust usually starts.
• A coat of wax in late fall gives the paint a layer between it and the brine.
• Touch up any paint chip before winter. A chip the size of a pencil eraser is an open door for salt.
• Rubber floor mats with raised edges trap the melt water instead of soaking it into carpet.

The one I wish I had done sooner is the paint chips. I ignored two chips on the rear wheel arch for a winter and by spring there was a rust spot under each one, both the size of a quarter. Fixing that properly is a body shop job.

If you park in a garage, park on the side away from the door. The floor near the door stays wet longer, and wet floor plus salty drip equals exactly the condition you are trying to avoid.