sounds like your temps were good. years ago you would do an induction time, some epoxys required it. i still do it, after its mixed i let it set in the mixing cup for 10 - 15 min. in real hot weather like you have 10 would work. your product info sheet won't tell you to do this its just something i carried over for years ago. i think it speeds the cure time, maybe i'm dreaming?
Jay D.

Jay, I don't think you are dreaming.... Chemistry friend of mine said when in doubt it's a good idea to do it anyway. You want the stuff to make sure it starts the cross linking process. We even do it with epoxy resins we use for repair. A little extra time in the cup greatly speeds up the overall cure. Even in fairly hot weather we give it at least 5 minutes or so...

this epoxy does have a 15 minute induction time and come to think of it that is one thing the tech at PPG never asked me about.
I am surprised with the hardener though because it just comes with the little metal screw off cap with no real seal to break yet I was told technically it's only good for 14 days once opened but I had read here or else ware that guys were giving cans a little shot of argon from there welders to help preserve there hardeners and I found a small can of argon on amazon that you use to preserve your favorite bottle of wine by giving it a shot once opened so you don't have to drink it all at once.
The techs only suggestion was to try and find a different distributor that has stock with different batch codes on the bottom of the cans and see what happens. The more you guys are talking the more I'm starting to think it may just be a time issue and it needs to cure more.

Well I thought I would put an ending post to this thread. Omni MP170 is some pretty tuff stuff. I gave my original test piece and samples made more time to cure and it is ridiculously hard. One sample made was just a piece of sheet metal scuffed with maroon scotch brite, cleaned with W/G remover and the epoxy is stuck to it hard and you really have to try to even put a scrape in it with a screwdriver. It also lays down nice and smooth. It's some good stuff.