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.
