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Which Sika primer?

B

Ben Ellis

Well Known Member
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I plan to attach my canopy with Sikaflex 295UV. I have already scuffed the canopy frame powder coat and applied epoxy primer and a 2 part single stage polyurethane. I didn’t want to try to paint the frame after attaching the canopy.

Based on my research, it seems the correct primer for the plexiglass is Sika 209D after scuffing.

For the painted surface, I'm seeing 2 different recommendations:

-- This indicates SP-207 by itself or SP-206GP with SA-100 activator.

-- This indicates SA-100 activator without scuffing or priming, or SP-206GP with
SA-100.

The second document is for marine applications and specifically mentions 295UV, so I’m inclined to follow that one. That would mean activator without primer.

Does that make sense? Would it hurt to use the SP-209D on the painted surface too?
 
I used the 209D on all surfaces after removing paint from the mating surfaces (-7 tip up aluminum frame and plexi). Not sure about the -8 frame though, but after scuffing and activator i think the 209D would still work. The bond will only be as strong as your weakest point, which is why I removed paint. I didnt trust the metal - primer - paint strength.

I would probably try to remove as much paint as possible.
 
I plan to not remove the paint so I’m focusing on the surface prep methods for painted surfaces, which is different than the method for bare metal.
 
wirejock said:
You have to use a primer. Sika won't stick without one.
Click to expand...

I thought so too but this chart seems to indicate that activator alone is the preferred method for application to painted surfaces. I’m going to ask Sika to clarify because I want to follow the instructions as closely as possible.
 

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Ben Ellis said:
I thought so too but this chart seems to indicate that activator alone is the preferred method for application to painted surfaces. I’m going to ask Sika to clarify because I want to follow the instructions as closely as possible.
Click to expand...
Try a test. Without primer, Sika rubs right off like that goop they put on credit cards in the mail.
 
wirejock said:
Try a test. Without primer, Sika rubs right off like that goop they put on credit cards in the mail.
Click to expand...
Depends on the paint. I got a small dab on the flat black glare shield - it was painted with rustoleum and the sika stuck to it tenaciously. Ended up sanding it off and repainting.

That said, I wouldn’t trust it and would clean it off and use the appropriate Sika primer. I used 205 on both aluminum and steel as per the Sika tech docs.
 
Side story but relevant caution to the thought about keeping the primer on.

I did an aeropoxy adhesive under my fiberglass to canopy on the 14, and I went to bare metal with it. I had primed the canopy skin, but used a stripper to get back to metal because I wanted to get the best bond.

I'm saying this because the paint stripper was good, almost too good, and it ran under tape lines a bit. My point, if you leave a primer on before the sika system, it's a potential weak spot under the adhesive (ie what if there's a strip and paint job in the future).

Just wanted to pass that on.
 
I scuffed the powder coat and put 209 primer on it. That was 16 years ago, with temperatures varying from 118F to 15F. No issues.

Nothing is stuck to that bare steel better than that powder coat, I wouldn't take it off. The Sika 209 sticks to it really well. I know because in places where I dripped, I can not get it off, even 16 years later.
 
I would NOT adhere a canopy to a painted surface. The bond is only as strong as the weakest link. Paint adhesion is typically not very strong and not designed to hold a 10 pound item in place at 200 mph, like an adhesive. The sika will adhere strongly to the paint, but the paint will not adhere strongly to the metal. The epoxy primer to metal is moderately strong, but the paint to the primer bond is weak.

A possible exception to this is powder coat paint. While not as strong as the sika, I suspect it is strong enough for that application.
 
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lr172 said:
I would NOT adhere a canopy to a painted surface. The bond is only as strong as the weakest link. Paint adhesion is typically not very strong and not designed to hold a 10 pound item in place at 200 mph, like an adhesive. The sika will adhere strongly to the paint, but the paint will not adhere strongly to the metal. The epoxy primer to metal is moderately strong, but the paint to the primer bond is weak.

A possible exception to this is powder coat paint. While not as strong as the sika, I suspect it is strong enough for that application.
Click to expand...
Have you ever tried to remove powder coat? Properly done, it is really bonded well.
 
scsmith said:
Have you ever tried to remove powder coat? Properly done, it is really bonded well.
Click to expand...
Only once (limited) and agree it seemed to be so. My gaurded response was only based upon my lack of knowledge as opposed to concern. I would trust your experience. Just didn't want to suggest things I have no experience with. I AM experienced with paint and Yes< i have removed it with razor blades and scrapers; Something I CANNOT do with powder coat.
 
I used Sika activator 205 and primer 209 on my 7 tipper (bare aluminum and plexiglass) and my 8 slider (powder coat, bare aluminum and plexiglass). Over 8 years on the 7 with no issues. Only one winter and summer on the 8 but no issues to date.
 
I emailed back and forth with Sika today and they told me the following. I'm not posting this to say that anyone did it the wrong way, just letting you know what the manufacturer said:

* This version of the document is the correct version to use and is intended for the US market. The other file I linked above is for the global market and the reason there are some differences between the two documents is because of "general availability of raw material"
* Either SP-207 or SP-206GP would work as a primer for a painted or powder coated surface
* They recommended SP-207 as a single primer that would work for both the paint or powder coated surface and the plexiglass. Application would be scuffing without activator on either surface.
* They explicitly said that 209D is not suitable for a painted or a powder coated surface or for bare steel (if you remove the powder coating)
* They said that 207 is suitable for a marine environment

Based on this, I decided to go with 207 and will probably end up removing the epoxy and taking it down to a scuffed powder coating.
 
Thanks for that information! If I ever do another build I will make that primer change. It is interesting that 9 years ago the local rep recommended the 205 and 209 which is why I used them then on my 7 and then did the same on my 8 (2 years ago). I will definitely keep an eye on the windscreen and canopy for any signs of delamination.
 
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