the only thing that has saved mine, is that I had it new since 1992. I painted the entire undercarriage with Rust oleum oil paint with Brush. got all of the fuels lines, brake lines, the links, the entire car. I even pulled the bumpers and painted the metal bumpers. I tried.
painting did not save the rockers!!!!!
The rocker panels always go on the B13's Its from underneath where the drain holes are where the seams come together. I removed from the driver door back to the rear fender. blasted the inner, painted and then got new metal and made my own rocker, using a baseball bat to bend and curve it out. I did not want to buy tools to do this shaping. I used my vise as the crimper and hammered it out. amazing it came out with hours of shaping. I drilled and pop-riveted the thing and ground them clean to teh surface. it worked.
Most of the car is in excellent shape. I have maintained it by painting over and over. I live in Southwest PA, so the salt was a killer.