OHW vs Primer vs AP
And I just happen to run into this situation.
I wanted to make a new thread though, the other one is way off topic
( http://k2forums.com/discussion/12292/ar-build-and-dip/p4 )
Not really...OHW is more costly than my NanoChem or Hydrosolutions...According to the adhesion tests we have done? Epoxy has better adhesion and THAT is the name of the game...
Price of OHW is too expensive for us to justify using it for production. We love it for small jobs in odd colors.
it's much cheaper to do a coat of NanoChem AP (about $30/gal) and coat of Aqualac (about $40/gal). AP takes literally seconds to dry. One guy coats a rack of parts w/ AP and it goes directly to the painter. Both are sprayed from pressure pots, so it's not like we are using the same gun and having to clean in between. I would honestly leave AP in a gun all the time like activator if we didn't have a pressure pot.
Yeah, I was always baffled why people make such a big deal out of spraying AP. leave it in the gun and dust it on while you are prepping the work. We times it, and it literally adds SECONDS to your process... even with large runs of parts. We looked at it as waterbased was so much easier to use that it was worth it.
Long read, but the background is important...
So, those PP welding helmets I've been doing. The guys business is slowly growing. I'm his "dipper". We have both learned a lot about processing this type of plastic.
The first helmet i did for him was a "tester" helmet. I used 2k epoxy primer, nanochem paint, express clear. We could NOT get the finished product to "fail". Forget normal adhesion test..we drilled holes thru it, cut chunks out of it, dug "groves" into it....
Although his business is growing, it's not really production. And the "painted" portion of his business sells less than his non-painted portion. A "wow that's cool!" vs "wow, that's more expensive!"
Sometimes weeks he may not sell any dipped ones, some weeks one, some weeks 3 or 4.
The designs he sells more of, we will make 2 or 3 at once, just so he has them on hand and ready to go (important fact).
So, for actual use, I switched to OHW. When doing just one or two helmets, it's just easier to pick up that PPS cup already full of OHW instead of mixing up a small amount of primer (man, that stuff is messsssy!).
This past weekend, we found that OHW does NOT have the same adhesion as the primer. He was re-doing some of the work he does on the finished product, when a small portion of the edge of the paint/clear pulled off. He gets aggressive with rivets/very powerful glue, and was removing some previous stuff.
So Friday night, we got together and tested things. A fully finished PP plastic piece, done with OHW and express clear, when we did a cross hatch test using duct tape, it WILL pull that area (and a bit more) off the helmet.
Now, duct tape is super duper strong. So we tested also with some 3M automotive masking tape I have, and it lifted a really small area, but it still lifted.
Using blue painters tape did nothing.
We tested several different helmets, done at different times, to make sure it was not a specific "batch" that had an issue. Every single one had same result.
I prepped one and used some 2k epoxy primer, then we went and had a few drinks while it dried. No dip or clear, just primer....and that primer would not come off.
This surprised us both. OHW is suppose to stick to plastic. That's why I use it.
Real life Usage..
He's got a couple of dipped welding helmets that he personally wears. Several of his friends have one. They have been wearing/using them daily for months now. Zero in the field issues with the OHW ones.
The cross-hatch with duct tape and 3M masking tape was an "in lab experiment". Not every day "real life". But.. it still failed. And like @K2Concepts said, it's about getting the BEST product out there.. not the "this will do" product.
More testing required...
I wonder if maybe, even though I'm blasting the parts, maybe it's not enough. Maybe it needs more for the OHW to bite.
The parts are also textured. Almost but not quite dimpled. I've wondered if maybe that could affect a cross hatch test.
I've got a lot of testing to do. He brought over about 20 "scrap" pieces from when he modifies the helmet.
I'm going to blast a part, then scuff it to put scratches in it, see if that changes the test results.
I've never used an adhesion promoter before. After reading what @MidOhioHydrographics and @WileECoyote , maybe I should go that route.
(I can really be long winded in some of these threads...)