Test Priming Day 2

Just after midnight  (about 7 hrs after spray) I checked the primer, scratch test has improved greatly but I was able to scratch it although considerable pressure was required (See bottom left corner). I work up this morning and checked the sample primer pieces. The primer has hardened to a point where it is really difficult to scrap with a finger nail (See bottom right corner). Almost no primer was scraped off the aluminum despite great effort.  When I got home from work (23hrs after spray) the test piece was not able to be scratched with a fingernail (see right side). Only when a screwdriver was used could the primer be scraped. (see center)

After 28 hours, I tried to remove the primer with a moistened towel. MEK and Acetone took the primer of the Aluminum very easily. The degreaser took a bit of rubbing in order for the primer to be removed. Gasoline had no effect on the primer. using a light colored cloth there was no transfer of dark primer onto the cloth...Didn't expect that. I prepped four new pieces of aluminum with Acetone, MEK, Degreaser and one just plain scuffed and wiped dry. Acetone seemed to evaporate almost immediately, more so than the MEK. I let the pieces dry outside for a while.  Then I sprayed two coats of Spray Max 2K epoxy primer. The primer application was really smooth and covered well. It occurred to me that in comparison, the Dupli-color required 2 heavy coats to cover, while the 2-part epoxy covered a bit better with only one pass. I waited 30min for the second coat. I noticed that the pieces took time to be dry to touch, after 30min the pieces where still a bit tacky.  (Note: The placement and timing of the scratches is the same as the sequence above.)  After 1 hour, the primer was able to be scratched with a fingernail. It seemed more like I was removing the top layer of the coat as I could not scrape down to aluminum. After  4 hours, the scratch test is similar to the Dupli-color after 24hrs. You have to press extremely hard to scratch with a fingernail, even then you only seem to be distressing the top layer....not quite breaking through the top layer.