SEM Trim Black Failure

[mluder]

About two years ago I refinished my louver, engine cover, and front window trim with SEM Trim Black.
The procedure for all 3 pieces of the windshield surround was the same. Stripped to bare metal, coasted with self etching primer, and then several coats of the SEM trim black from a spray can.
A couple of weeks ago I discovered this...

35805 :sad30:

The side pieces are fin - no cracking or crazing. I know the top is stainless steel and the sides are aluminum. Is this the effect of too much expansion and contraction from the heat of the sun? Anyone else seen this or have theories?

Cheers
Steven

[sdg3205]

Not enough prep with tiger blood for "winning" results.

I see paint fall off these pieces on a lot of cars, including mine. Perhaps it's the just the physics these pieces have to endure?

[mluder]

Not enough prep with tiger blood for "winning" results.

I see paint fall off these pieces on a lot of cars, including mine. Perhaps it's the just the physics these pieces have to endure?

Yeah... I'd be curious to measure temperature differentials between the side trum and the top to see if the steel retains more heat than the aluminum. Or if the metal just moves more...

Cheers
Steven

[Delorean Industries]

Yeah... I'd be curious to measure temperature differentials between the side trum and the top to see if the steel retains more heat than the aluminum. Or if the metal just moves more...

Cheers
Steven

This is common on these components if costs are not consistent. You also need to provide at minimum a red scotch beet pad scuff finish to the primer.

[David T]

This is common on these components if costs are not consistent. You also need to provide at minimum a red scotch beet pad scuff finish to the primer.


It is either improper prep or too many coats of paint. Hard to tell from the picture.

[kings1527]

The only place I didn't have the best results with Trim Black was on the windshield trim. It was very difficult to get the paint to adhere well to the stainless trim. It's held up decently over the past two years or so but I'm definitely going to take them to an autobody shop and have it done right. Someday.

[1batt4u]

So I am about the tackle this. I sanded the fiberglass body section using 220 sandpaper then a green pad to smooth it out. Then I degreased everything and washed everything off. Everything is taped off.

I bought SEM Trim Black Primer in a can not aerosol http://www.summitracing.com/parts/smm-39671 and another can in the SEM Trim black paint to top it off http://www.summitracing.com/parts/smm-39141

I will be doing the fiberglass body, trim around the front windshield, license plate trim, plastic pieces on stainless panels, radiator cover, rear engine cover and louver, and the engine air box.

PLEASE give me any pointers or recommendations, as I want this to go correct and not have any problems now or in future.

I do have a few question.

1. The primer can writes 25-30 psi from non-HVLP, 8-10 psi from HVLP. I bought a spray gun from Harbor Freight http://www.harborfreight.com/heavy-duty-air-paint-spray-gun-97855.html The gun writes to use between 60-115psi. Now what would I adjust my air compressor to in this case??

2. 2-3 light coats, 5-10 minutes flash time. I take it they mean each coat should be within 5-10 minutes and all that depends on the temperature? Here in NY its high 80's and dry, no humid these past few days.

3. Topcoat after 1 hour and within in 24 hours. What do they mean by that exactly, topcoat after 1 hour of finishing the primer or if not within 1 hour to wait 24 hours later??

If someone can explain in details, I want everything to go right.

Thank you very much!!

[kings1527]

So I am about the tackle this. I sanded the fiberglass body section using 220 sandpaper then a green pad to smooth it out. Then I degreased everything and washed everything off. Everything is taped off.

I bought SEM Trim Black Primer in a can not aerosol http://www.summitracing.com/parts/smm-39671 and another can in the SEM Trim black paint to top it off http://www.summitracing.com/parts/smm-39141

I will be doing the fiberglass body, trim around the front windshield, license plate trim, plastic pieces on stainless panels, radiator cover, rear engine cover and louver, and the engine air box.

PLEASE give me any pointers or recommendations, as I want this to go correct and not have any problems now or in future.

I do have a few question.

1. The primer can writes 25-30 psi from non-HVLP, 8-10 psi from HVLP. I bought a spray gun from Harbor Freight http://www.harborfreight.com/heavy-duty-air-paint-spray-gun-97855.html The gun writes to use between 60-115psi. Now what would I adjust my air compressor to in this case??

2. 2-3 light coats, 5-10 minutes flash time. I take it they mean each coat should be within 5-10 minutes and all that depends on the temperature? Here in NY its high 80's and dry, no humid these past few days.

3. Topcoat after 1 hour and within in 24 hours. What do they mean by that exactly, topcoat after 1 hour of finishing the primer or if not within 1 hour to wait 24 hours later??

If someone can explain in details, I want everything to go right.

Thank you very much!!

I did everything out of a spraycan for my project, which was pretty much the same as what you have going on. With the exception of the windshield trim, as I mentioned before, I used a different adhesion promoter and everything has held up real well over the past three years or so which obviously includes multiple washes.

http://www.amazon.com/gp/product/B005IUBMS6/ref=pd_lpo_sbs_dp_ss_3?pf_rd_p=1944687562&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B002GUGH04&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1DS3Y5HWW86J8RTD56Y5

I'd recommend wiping the area down after sanding with acetone to really strip and clean the area down to the base. As with any kind of painting, prep is key. Trim Black goes on real thin so if you have any kind of sanding marks left behind, TB won't cover it up. So be sure to finish everything off with a real fine grit. It sounds like you did with the green pad. In other words, whatever you have left behind is what you'll have after the application of TB.

TB dries real fast. I was applying a coat and then another around 10-15 min later. I'd keep doing that until I'd decided that I'm happy with it. As with any kind of painting, use several light coats rather than a heavy coat.

Also, if your air box is really bad to begin with, consider just buying a new one instead. That's what I ended up doing. Those don't really clean up well, even with TB. But you might as well give it a try since you have all the equipment set up.

http://store.delorean.com/p-6352-air-filter-assembly.aspx

Good luck. Believe me, TB is incredibly forgiving and easy to work with. It'll look pro when you're done.

[1batt4u]

Thank you for the info!!

What kind of acetone do you recommend?

What I mentioned above about priming and then topcoating. Do I wait an hour later or 24 hours later?

Thank you again!

[Ron]

+1 David T, on the cracks shown in the OP being too many coats of paint (at the same time. "Checking"/"Crowfoot").

=====

Billy,

I'm not a pro-painter by any means, but $.02:

1. The primer calls for 25-30 psi from non-HVLP (the type you purchased) and the gun calls for 60-115psi. Not a good match (out of working range).

2. 5-10 minutes flash time means you should wait 5-10 minutes between coats.
When the primer dries to a point where it is still wet enough for the next coat to bond well, yet dry enough to apply another coat without running, you can usually see it flash (sometimes a subtle change in color-shade).

3. Topcoat after 1 hour and within in 24 hours means to wait at least one hour for the primer to dry and apply the top coat (color), but have it done before 24 hours.
Too soon, you dissolve the primer, etc. Too late, you don't get a good bond...

[DMC5180]

Acetone is acetone. Any brand will do. The brand most often seen in hardware stores is Sunnyvale IIRC.

It means let your intitial coats set up for at least 1 hour before applying the final top coat. You have up to a 24 hour window in which to apply the final coat without the need to scuff prep for adhesion. Basically the initial coats remain in a green stage cure process for the first 24 hrs.

[1batt4u]

So I tested both the SEM primer paint and top coat paint using an HVLP spray gun.

Primer came out great, smooth finish, top coat came out good, but sort of a texture finish. I did buy the aerosol spray cans a few years ago, did some tests and same with that, it came out sort of a texture look.

Is this how these SEM black trim paints always come out?

[mluder]

So I tested both the SEM primer paint and top coat paint using an HVLP spray gun.

Primer came out great, smooth finish, top coat came out good, but sort of a texture finish. I did buy the aerosol spray cans a few years ago, did some tests and same with that, it came out sort of a texture look.

Is this how these SEM black trim paints always come out?

Yep... The trim black definitely has a bit of "texture" to it. As I understand it can be varied depending on the distance you spray from - Farther away = more texture, etc. That being said, a few washes and the texture starts to knock down.

Cheers
Steven

[1batt4u]

Yep... The trim black definitely has a bit of "texture" to it. As I understand it can be varied depending on the distance you spray from - Farther away = more texture, etc. That being said, a few washes and the texture starts to knock down.

Cheers
Steven


I used a cap off a aerosol spray can to pick up the paint from the can and pour into the HVLP spray can. I was looking at the cap with paint all over it and it has a very nice smooth finish, no sort of texture or anything. Looks really good!

I guess it all about adjusting the spray gun and distance. I was actually kinda far, because all the aerosol spray can I use write keep 10-16" away from part when spraying. I thought the same here, but the videos I checked out using a spray gun everyone was so close. Some mentioned about being 5cm(2in) away from part. So I'll test different psi adjustments and go closer.

Thank you!

[cpistocco]

I used a cap off a aerosol spray can to pick up the paint from the can and pour into the HVLP spray can. I was looking at the cap with paint all over it and it has a very nice smooth finish, no sort of texture or anything. Looks really good!

I guess it all about adjusting the spray gun and distance. I was actually kinda far, because all the aerosol spray can I use write keep 10-16" away from part when spraying. I thought the same here, but the videos I checked out using a spray gun everyone was so close. Some mentioned about being 5cm(2in) away from part. So I'll test different psi adjustments and go closer.

Thank you!

The more you reduce the paint, the less "bumpy" it will be....BUT do not over-reduce (It may run or lift your primer). Also, you should never put topcoat directly over a self-etching primer. You need to seal it first.

[mluder]

The more you reduce the paint, the less "bumpy" it will be....BUT do not over-reduce (It may run or lift your primer). Also, you should never put topcoat directly over a self-etching primer. You need to seal it first.

I don't recall the instructions for the primer indicating that... Though Josh does mention earlier in the thread that you do need to scuff the primer with a red scotch-brite prior to topcoat.
I would think a sealer would counteract the purpose of a primer - to give something more mechanical for the top coat to bond to. Can you elaborate?

Cheers
Steven

[1batt4u]

I bought SEM primer. It doesnt mention anything like that. Just to wait 1 hour to 24 hours to topcoat it