So, you've tried them all, and SPI was the best? What attributes did it have that other epoxy primers didn't have?Hands down...SPI epoxy primer...Just follow the directions at their website...Additionally they are phenomenal at answering their phone...Been doing business with them for years.
This is all true of SPI, except price wise is low.Advantage is you can use it as DTM epoxy or as a sealer before paint just by adjusting the mix ratio. Second advantage is you can get it in various colors to set up your base foundation before painting which will save you on Amount of paint applied to achieve full color coverage. Price wise is medium.
Just so people reading this will understand the terms correctly, its called "induction period", not "incubation period". The induction period is the time interval needed to start a crosslinking reaction between the epoxy base and the catalyst. I've used it as a moisture barrier on bare metal and as a sealer before paint for many years, with excellent results. I recently discovered that it also wet sands nice.I've used about every epoxy primer out there. Like Rick said the PPG series DP original epoxy was very good. The DPLF is terrible, adhesion is poor and you had to apply primer or top coat over within 24 hour or had to rescuff first, As well as the price is way up there.
Nason is ok, but the incubation waiting period doesn't fly in my shop. Works better as sealer before paint than an epoxy on bare metal.
Dupont's series is ok, but time consuming as well. Lays down fairly flat to reduce sanding needed. Again the price is up there.
SPI applied too dry for my liking and sanded poorly. Their build primers were similar. Price was low compared to others.
Sherwin Williams had adhesion issues while blocking it out.
Valspar (and House of Kolor) Epoxy's work very well, lays down beautifully, no incubation or wait times, can apply high build primer directly over it after 20 minute flash time (just as you would paint). Advantage is you can use it as DTM epoxy or as a sealer before paint just by adjusting the mix ratio. Second advantage is you can get it in various colors to set up your base foundation before painting which will save you on Amount of paint applied to achieve full color coverage. Price wise is medium.
A lot depends on the sprayer, incubation times, re-coat windows and the amount of work you want to do after the application.