As far as sitting LEFT ALONE in a B117 salt bath spray, yes np3 and most every other soft coating including Cerakote will littlest any PVD that I'm aware of. But PVD has the ability to soak up and retain oil, providing a near impenetrable barrier against corrosion. And what happens when you scratch a soft coating, exactly how much corrosion resistance will that coating provide?
I was simply stating(to a man seeking better scratch/wear resistance) that PVDs fill that role better, in the real world, where people actually maintain their firearm and don't plan on leaving it submerged in 120° salt water for 3.5 years and expect it to run afterwards.
Also, there are many different "DLC" formulas, each with their own strengths and weaknesses, though comparable in composition. "We" don't have a proprietary anything as "We" aren't buying a $5m PVD machine anytime soon. However the company that performs that service for us does have their own formula, and my research indicates that it is the most ideal for the task.
The numbers I was"throwing around" were being used to educate those unfamiliar with the coatings on the potential gains in scratch resistance alone and as long as the numbers are correct there shouldn't be an issue "throwing them around". After all "numbers" are the only reason you know NP3 Plus offers better corrosion resistance. Heck, "numbers" are the only reason that corrosion test exists in the first place!
NP3+ is a phenomenal coating which is brought to you by one of the most successful Vet-Owned manufactures in the industry, and I'm a huge fan, but to those that may be seeking a black scratch resistant coating, I know if none better than the aforementioned.
I've seen several guns that had a PVD finish that was worn all to hell. Kydex is "static'y", and that attracts dust. Dust particles are UUGELY larger than the coating's thickness. All it takes if for that dust particle to dig under that micron thickness coating and there you go. Scratched. These coatings are engineered for surface abrasion applications where "like" components are sliding or rolling on each other in controlled (generally not open to the atmosphere) conditions. They have been used for over 30 years as cutting tool coatings and only "relatively recently" on machine components.
Also if the coating is porous and diamond hard, that just means that the pores that fill up and hold oil leave a pathway for moisture to get in. That oil isn't an "impenetrable barrier" by any stretch so in the pores themselves there is no hardness. FYI, I personally ran a ASTM B117 salt fog cabinet 24/7/365 for several years. I have years of experience with various engineered coatings in the aerospace and oilfield industries. All these coatings are great for their various purposes (usually wear resistance) but keeping guns looking pretty isn't what they excel at or are even developed for. Real world is different when you start drawing from a holster, if you leave it in the safe and take it out to look at it once a year to look at it, then yes, they are all fabulous. I'm not saying to ignore the specs and testing, but just keep this in mind when looking at them. There's a chit TON of marketing behind them.