PA, especially northern is in the perfect location for constantly going between freezing and thawing. This means water will melt often and react with the salt. If it stays below freezing/above often it would have less of a effect.

I'd recommend undercoating the bottom, wheel wells, and inside rockers of your vehicle with a lanolin based spray. It'll keep any moisture/air from your frame. It'll save money in the long run. That way all you have to do is spray down the exterior and not worry about underneath