Agree with the treating the bolt heads Davw BUt and its a BIG BUT what lies beneath the running board is the rusting screw thread and nut....suggest remove these and put in stainless M3 by 10mm countersunk screws and faten with stainless nylocs!
much better job abd you wont need to revisit this job ...
its done for good.
Stainless screws with with an ali superformed wing
