I've had my last three vehicle purchases rustproofed by Henderson Bros Rustproofing in Midland MI. I little pricey but they do free inspection/touch ups every three years.

The frame on my 2016 is still just like new after 6 michigan winters

https://www.hendersonbrorustproofing.com/

But I agree the road departments need to switch to a more environmentally friendly de-icing agent.