Tips for spray painting fender

[D'z Nutz]

I have a motorcycle fender I need to paint and I just wanted to confirm I'm gonna be doing this right. I didn't want to hijack ExtraSlow's thread so I just started my own.

From what I've read around the net, here's what I gathered. Please feel free to correct me or make suggestions since I've read a lot of contradictory information.

1. Don't spray on days colder than 60F (~15C) and not when there's humidity.

2. Warm the cans in hot water for a more even spray.

3. The (steel) fender will have the original paint sandblasted off and will have a decent scuff for the primer to stick to. From what I've read, I should be using epoxy primer and not self-etching. Apply a light coat, wait 10 minutes, apply a thicker coat, wait another 10 minutes, then apply the final coat. First question: I'm reading I should be letting this dry from anywhere between 1 hour, 3 hours, to over night. Suggestions?

4. Sand primer. Should I be sanding with 400 grit or 800 grit? I've read both.

5. A question on Abeo's suggestion from the other thread:


Originally posted by Abeo
What I would do:
Sandblast the rust
epoxy primer
fill the pits with filler (if needed). Scuff the rest of the bumper
filler primer, block sand
seal the filler primer, base, clear (could use single stage since it's a solid color)

Assuming the fender has no gouges or scratches, can I skip the filler and sealer primer? Or will I have to do that regardless? Some sites I've read didn't even mention the filler/sealer primer and went from primer straight to base coat.

6. Apply the base coat. Like the primer, apply a light coat, wait 10 minutes, apply a thicker coat, wait another 10 minutes, then apply the final coat. Again, I'm reading I should be letting this dry from anywhere between 1 hour, 3 hours, to over night. I've even read letting it cure for a few days before applying the base coat. Suggestions?

7. Sand the base coat. Again, 400 grit or 800 grit?

8. Add clear coat. Like the primer and base coat before it, apply light coat, wait 10 minutes, apply thicker coat, wait another 10 minutes, then apply the final coat. Let it dry/cure.

9. Sand out dust and bugs and whatever from the clear coat.

10. Polish and wax.

11. Install fender on bike.


How does that sound? I'm not expecting this to be perfect, but I don't want it to look like ass either and chipping/peeling within a year.

Thanks guys.

[Abeo]

Just to clarify my previous comment, most paint out of cans are 1k (non-catalyzed). There are some Eastwood products that are 2k (catalyzed) spray cans. The difference between a 1k and 2k is that any solvent on a 1k will soften and melt the paint/primer. This includes any gas dribbles, or topcoats. If you try to spray 2k over 1k, then you run the chance of melting into the 1k paint and causing all sorts of headaches. There are some people who are able to use 1k products and then topcoat with 2k, but it really requires knowledge of the products and/or experimenting.
An exception to this is things like Por15, which is a 1-part paint but is moisture (from atmosphere) cured. It's prone to lifting in sheets if it isn't applied right too.

A catalyzed, chemical cured paint is stable once the paint has cured. A 1k paint will never be.

A sealer is used (usually a thinned out epoxy primer) to lock in any primers, filler, etc before basecoat, and to provide a uniform color to put the color coat onto. If you do a wet-on-wet application, it provides even better adhering to the basecoat. Sometimes the basecoat will react to some of the weaker filler materials if you are spraying it right on, or some surfaces absorb the solvent in the paints at a different rate, so having a sealer coat is just extra insurance for a good job and not to re-do.

If it's a straight color change, there are no gouges or scratches, you could just scuff and color coat it. If you are going from dark to light, a light colored sealing coat would be needed.

I worked at a bodyshop for years, but I am really a beginner. I studied a while before trying my hand at a real paint job, you can see my messups and what I eventually ended up here: https://www.autobody101.com/forums/viewtopic.php?f=5&t=25873

That site is a great read to get the steps on what to do.

[Abeo]

I'll come back to the thread later and answer your questions a bit better, but:


Originally posted by D'z Nutz
I'm not expecting this to be perfect, but I don't want it to look like ass either and chipping/peeling within a year.


With enough time, prep and being careful, you can get it very close to perfect, even as a beginner. Just expect to learn along the way.

[ercchry]

Vinyl wrap... a fender would be super easy

[carson blocks]

Originally posted by ercchry
Vinyl wrap... a fender would be super easy

Wouldn't vinyl have different light absorption etc. than the 'matching' painted surfaces, even if the colour was dead on?

[ercchry]

Originally posted by carson blocks


Wouldn't vinyl have different light absorption etc. than the 'matching' painted surfaces, even if the colour was dead on?

Well neither option would be a perfect match... but I have a buddy who wrapped the chrome on his truck to "colour match" the bumpers to body... and it's honestly probably better finish than any driveway paint job, but yeah you can tell something is still off, but that's paint butted right up to vinyl where as with a motorcycle fender it's going to be hard for the eye to tell since you have such a large break between painted surfaces

[mr2mike]

High build primer is your friend.
Makes life easier for sure.

[D'z Nutz]

Thanks for the response.


Originally posted by Abeo
If it's a straight color change, there are no gouges or scratches, you could just scuff and color coat it. If you are going from dark to light, a light colored sealing coat would be needed.

The fender's original colour is black and it's going to be repainted back, but the reason for me wanting to sandblast it and start from scratch is because

1) I chopped the fender so that it's a little shorter than stock and the chopping exposes the bare metal on the edge, and

2) there's a bit of pinstriping underneath the original clear coat that doesn't match the rest of my bike so I just want it straight up solid black

Should I rethink the sandblasting idea and just paint over the original finish?

[Abeo]

If it's rusty, or the existing coating is super hard and chemical resistant, or chrome, then I'd sandblast. If it was just cut and I was happy with the existing paint, I'd feather edge the cut area and epoxy prime a little portion of it. If it wasn't rusty and the paint is questionable, I'd chemical strip it (leaves a much nicer surface finish and you don't have to worry about warping... plus sandblasting is messy).

On my car's fenders, I found some questionable work under a wrap, so I did a chemical strip at home. I just hit it with my DA and some 120 and it was ready for epoxy primer (aside from the filler/welding needed). Sandblasting leaves a rougher profile so you have to spend more time blocking out a high build primer (which means more chances to create waves, and more time spent on it).

[Abeo]

Originally posted by D'z Nutz
1. Don't spray on days colder than 60F (~15C) and not when there's humidity.


If you are spraying 2k products, you can change the speed it cures at with different activators for different temperatures. Also, pay attention to the surface temperature, not just air temp.




2. Warm the cans in hot water for a more even spray.



Make a bit of a difference. One thing that makes a real difference is shaking for a long ass time. Sometimes the tips just suck, so I steal one from a can that sprays better.




3. The (steel) fender will have the original paint sandblasted off and will have a decent scuff for the primer to stick to. From what I've read, I should be using epoxy primer and not self-etching. Apply a light coat, wait 10 minutes, apply a thicker coat, wait another 10 minutes, then apply the final coat. First question: I'm reading I should be letting this dry from anywhere between 1 hour, 3 hours, to over night. Suggestions?



The longer you let dry or cure, the less of a chance you'll get scratches telegraph through later after the solvent evaporates out. Trapping solvent in is a bad thing, so stay away from heavy coats or coats too close to each other. Stick to the paint recommendations.




4. Sand primer. Should I be sanding with 400 grit or 800 grit? I've read both.


You should go progressively up. For black, I'd have a final sand at 600.
http://www.collisionblast.com/2012/07/15/what-grit-of-sandpaper-should-i-use-for-auto-body-and-paint-work/




6. Apply the base coat. Like the primer, apply a light coat, wait 10 minutes, apply a thicker coat, wait another 10 minutes, then apply the final coat. Again, I'm reading I should be letting this dry from anywhere between 1 hour, 3 hours, to over night. I've even read letting it cure for a few days before applying the base coat. Suggestions?



That;s about right, but you have to pay attention to the way it's laying and how fast it's drying. For 2k, once it's tacky it's about ready for the next coat.




7. Sand the base coat. Again, 400 grit or 800 grit?



I wouldn't unless the base coat set up hard. But if you want to, 800 or so. You can't sand metallic base coats. Think of clear as the same as base coat, but with clear pigment.




8. Add clear coat. Like the primer and base coat before it, apply light coat, wait 10 minutes, apply thicker coat, wait another 10 minutes, then apply the final coat. Let it dry/cure.



Yup... just really make sure you don't lay it on heavy.




9. Sand out dust and bugs and whatever from the clear coat.



Eh, I'd just try my best to avoid runs or dust. Sanding out imperfections isn't the easiest thing. Also, runs stay gummier than the rest of the paint, so that makes it tougher. Some people knock down the runs and let the solvent evaporate before polishing it any further.




10. Polish and wax.



...if it needs it :thumbsup:

And some general tips:

It's 95% prep, and 5% of actual spraying.
You can't have enough light.
Bare metal, filler, primer and paint all sand at different rates, so if you aren't careful you could end up with waves after sanding.
2k paint is no joke. It has some nasty stuff in it.
A $40 resporator will keep junk out of your nose and lungs.
POR15 doesn't come off skin once it's cured. It has to wear off.

[D'z Nutz]

Awesome, thanks for the suggestions Abeo!