humidity + primer adhesion

[prkaye]

Long (and generally frustrating) day in the shop working on the flaps today. For some reason I had real problems getting my self-etching primer to stick to anything today. It's the same stuff I've been using all along (Canadian Tire stuff)... rattle cans.

It poured rain here for about 12 hours straight ending this afternoon... wondering if the high humidity could have anything to do with it? I had the garage door open. The cooler temperatures (maybe 17 degrees C) might also have had something to do with it.

I'm wasted a lot of primer today. Actually, I've been going through an insane number of rattle cans in general... dozens. They're expensive... between 10 and 20 bucks a pop. I wonder if I should consider another product, and/or modify my technique?

[vlittle]

Phil, I've had the same problem on the wet coast. Don't shoot when the dew point and ambient temperature are close.

Sometimes, when I've had to prime small parts at the airport, I put them on the compressor to warm up, shot the primer, then put them back in the compressor room to cure. Works in a pinch, but not for large parts.

What works really well is to set up a paint booth in the kitchen. Temperature controlled, with lots of ventilation and a good source of heat. The bonus is all of the extra rooms in the house you get to store parts when your wife takes the kids and leaves you.

Vern

[rv8ch]

Originally Posted by vlittle

...What works really well is to set up a paint booth in the kitchen. Temperature controlled, with lots of ventilation and a good source of heat. The bonus is all of the extra rooms in the house you get to store parts when your wife takes the kids and leaves you.

Ha! Not my wife, she'd throw me and the airplane parts out!

[dsyvert]

Phil,

I ran into the same problem the first time I primed. I spoke to a SW aviation distributior. They have the following guidelines for their products.


1) The temperature-dew point spread must be at least 10F degrees.
2) The temperature must be at least 65F.


I got some charts from him of what the acceptable conditons of priming are for applying epoxy primer epoxy.

Dave Syvertson
RV10 QB

[az_gila]

Phil,
The AKZO data sheet uses 59 F - 95 F and a Relative humidity of 35% to 75% as recommended conditions.

When I lived in LA, and painted outdoors just before sunset as the humidity went up, I noticed that the primer would seem to absorb water, and make sort of bubbles that didn't stick.

I think the epoxy primers are somewhat hygroscopic...

gil in Tucson.... where getting the RH up to 35% is the usual problem.... ...except for this month...