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Does rattle can primer have a shelf life?

J

jcfields

Member
I noticed the other night when I was working on the rudder spar that the primer was getting really scuffed up. So, out of curiosity, I ran my fingernail over a spot, and the primer scratched right off :eek:!!! I tested this in a few more spots, and everywhere I scratched, the primer easily came off. I have some other tail parts that were primed several years ago (I bought the tail kit "gently used" from an ex-builder), and their primer application seems to be holding up. All parts (old and new) were primed several weeks ago using rattle can SEM self-etching primer, and the primer I'm using now is the stuff that was given to me by the previous builder (and is thus several years old). It sprays on fine, and looks nice, but I thought it was supposed to be a little harder to scratch off...

Anyway, I'm just trying to figure out what's going on here. Should I toss this stuff and get something else? Anybody had this happen while using SEM's products? Could this be temperature related (even though it's not that cold here in TX)?

(And BTW, I'm not trying to start any rattle can vs. etch/alodine/prime debates here. I'm going rattle-can all the way - well-except maybe in the wings around the fuel tanks - jury's still out on that one...)
 
Good Question

Not sure about performance in service once applied but I've just tossed two "new" cans of Marhyde I couldn't even get to spray after shaking for what seemed like hours. I bought them as a six pack a while ago. The other four cans worked great.

Jim Sharkey
 
I suspect that if it had gone bad you would have noticed that something was not right during the application. Perhaps the surface was somehow contaminated, how did you prep the part before priming?
 
Time is the secret, even then it's still not the most durable in comparison. FWIW I just used some acetone to remove some SW 988 applied about 2 years ago in an area that need to have epoxy applied...it took much more effort than I thought but alas...I was able to remove it after a few minutes of rubbing with a paper towel and acetone. The AKZO stuff I shot in the tail is harder than nails...So..shelf life? Unless it's been previously sprayed..you have many years to expiration.
 
Moisture?

I took a perfectly etched/washed cherokee rudder one summer eve and hung it and shot it with zinc primate. Looked great. Then the sun went behind the trees, the temp dropped, the aluminum went dewy and the primate fell off. Go figure.
 
aerhed said:
I took a perfectly etched/washed cherokee rudder one summer eve and hung it and shot it with zinc primate. Looked great. Then the sun went behind the trees, the temp dropped, the aluminum went dewy and the primate fell off. Go figure.
Click to expand...

Zinc primate....I'd say that spray can must have been genuinely prehistoric and obviously well past it's shelf life.:D
 
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SEM,,,,have seen it roll up and fall off like leaves, but only when painted on alu that has been alumnaprepped with etch.???? will happens every time for me. i never mix etch of any kind now. one will remove the other. IME
 
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