Frame rot: how far to keep driving?

I keep my frame coated w Fluid Film. It’s not a ‘one time’ thing either. You need to reapply each fall and hit it along the winter season as needed. In rust prone States, its more of a routine and part of the upkeep with TJ’s, unfortunately. CRC also makes a rust inhibitor that seems to work well too. Im absolutely doing a side by side comparison of the two products this summer on painted and bare steel.


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soo in an effort to see how long I can go, due to military and work requirements, I check it daily for severity. while checking last night, I checked and happen to look further back and noticed a hairline crack at the frame/upper control arm mount. SON OF A NUT TREE!!! so I am now more concerned with this than the frame. I think I will see if the wife will swap me titles, so I can go back to my Ammo can TJ for a DD. Then I can park the Sahara until I can get to the repair or frame swap..
 
I’ve heard those same complaints, and the only reason I can think of is the owner badly scraped the coating off the frame or underneath somewhere and didn’t take it back to have touched up which they tell you before and after you have it done. It’s not impenetrable, but if handled correctly I don’t see how it could be worse.

it isn't impenetrable and nothing is perfect, not even if you do it under an off the lot vehicle, but just the nature of undercoating, texture wise, makes it have the ability to " hide " whats going on under it more than paint. Most the time, by the time you see rust with undercoating, its way too late. I'll stick to my gloss paint and fluid film combo, 21 yrs old and still rust free.....