NSG 370 is to the AX - 15
As the owner of an LJ with the former, I've never claimed it to be superior to anything. In fact, I consider it to be the weakest part of the vehicle, but it's what they came with in '05 and I wasn't having an auto gearbox, so I'm living with it. Think you've got the wrong guy on that one. That said, I do prefer six speeds to five speeds if given the choice.
First off, don't be fooled by appearances. Just because a coating is flat red/brown, flat grey or flat black is not an indication of what the actual product is.
The products you listed are two part catalyzed epoxy primers and are applied with professional spray equipment. Regardless, they are not topcoats and are very susceptible to breaking down under UV exposure. They are part of a system and not weatherproof in and of themselves.
Many primers up until the early 80s (at the least) were lacquer based and uncatalyzed, though enamels (followed soon after by urethanes) had been introduced and were becoming more available to consumers. Most cars running around with primer as a topcoat in the '70s, '80s and '90s were using neither epoxies nor catalyzed products as anything from a rattle can was likely a lacquer or enamel based and set by solvent evaporation, not chemical hardening. Not durable or weatherproof finishes by any measure.
Sikkens did have a heavy build filling primer/surfacer back in the late '80s, the product name escapes me at the moment, which was weatherproof for a period of time after setting, provided that it wasn't sanded. Still not a topcoat.
FYI, just because you can't see rust or see bubbling under a coating doesn't mean something isn't rusting. Unless you are in 0% humidity, if you sand a panel to bare metal and do not protect it shortly thereafter, it will start rusting. It's called flash rust, is not something you can necessarily see unless in an extremely humid environment and can have an effect on adhesion of subsequent coating applications if not addressed. The use of epoxy primers in structural steel and ship building is for this very reason and not meant as a permanent coating or a solution to rust prevention. There are some steels that are designed to develop rust as a protective coating, but that is for another discussion. As for ships, doesn't matter what you coat them with, they rust.
