Sanding+primer vs. just primer

Planning on painting my camper shell black pretty soon here, it’s currently green. Does sanding it before primer and paint really make all the difference or would primer and paint be just fine? Who’s done this? Thanks

 

I don’t have a lot of experience with automotive paint, but a universal rule is pigmented paint needs tooth to adhere. I just color matched my chrome grill and the paint and primer peeled up on a few edges where I missed sanding and it looks great on the rest that got hit with a 320 grit sandpaper. While chrome is more slick than paint, I would be willing to bet you would get the same undesirable results if you didn’t at least give the surface a little tooth. Especially over a clear coat.

Just an FYI, there are lots of threads on how to properly paint on here, but this guy did a great write up on how to properly do a rattle can job: https://www.tacomaworld.com/threads/step-by-step-how-to-spray-paint-with-quality-results.400182/

 

You absolutely need to sand. Number one rule of painting anything is preparation.

Without proper preparation, imperfections will show in the paint. I painted my toolbox how an autobody shop would do body panels, let me run you through the process as painting a camper shell will be very similar:

I used a pneumatic Dual Action sander which is what body shops universally use, you need a high capacity high-CFM output air compressor to run one. You can get by with an electric random orbital sander to some extent.

1. Strip all old paint and rust off with a paint disk or a flapper disk
   
2. Degrease and clean all surfaces
3. (Optional) Bondo, Body Filler, and Glazing/Spot Putty - I had no damage on the toolbox so I omitted this step
4. Sand with 40 Grit
5. Sand with 80 Grit
6. Sand with 120 Grit
7. Sand with 220 Grit
8. Sand with 400 Grit
9. 1st Coat Self-Etching Primer
10. Wet-Sand with 400 Grit
11. 2nd Coat Self-Etching Primer
12. Wet-Sand with 400 Grit
13. 3rd Coat of Self-Etching Primer
14. Wet-Sand with 400 Grit
15. 1st Coat Base Coat
16. 2nd Coat Base Coat
17. 3rd Coat Base Coat
18. Wet-Sand with 400 Grit
19. 1st Coat Clear Coat
20. 2nd Coat Clear Coat
21. 3rd Coat Clear Coat

I should add some people choose to wet-sand in between every single base coats and clear coats, but I chose to not do this due to time constraints. Tack rags are very helpful in gathering all dust and debris.

This isn't a perfect set of instructions but it's what I did based on what I've read up on auto-body work. Totally not an expert, this is just the process I went through. Like I said, preparation is the number one factor in having a good looking paint job. If you slack on the prep you will definitely see it and it will show through the paint.

 

Forsure. Thanks for the link!

 

Yes you do. Just bought a door and they didn't sand it before they had repainted it and the newer paint is flaking off and the original paint look perfect underneath

 

Absolutely sand before painting.

Like Mr Flux capacitor said, prep is key.

At a bare minimum, you need to get the clear coat off, and "scratch" the existing paint to give the new primer something to latch onto. But for best results it ALL has to come off, at least down to the original primer coat. It's a PITA, but you get out what you put in, so if you want it to last and not look like ass in a couple years (or months, lol), take your time and do it right.

Ideally, you'd remove any and all hardware, windows, lights, etc... before getting started. Do all your sanding etc... outside, but be careful with painting outside as you'll get all sorts of leaves, dog hair, pollen, etc... encased in your paint if not careful.

 

Sanding between coats isnt just overkill, it's a total waste of time and material. Light sand the existing to remove gloss, clean well and start spraying. If you want glass smooth finish go extra on the clear and color sand. Factory paint is far from smooth, lots of orange peel.

 

Depends on the quality of the finish you want, and how much time to have to spend on the project. Factory paint isn't usually very smooth because they don't typically sand in between their coats (usually too expensive/time consuming).

But slapping 25 clear coats on doesn't give you a glass smooth finish, that just makes it shinier.

Paint is not applied perfectly smoothly, so if you want a smooth finish, you HAVE to sand in between coats.

Especially when the OP is looking to paint the shell BLACK, extra time and attention to detail will make the results that much better. Black is extremely hard to make look nice.

 

you didnt mention what the shell is made of... if it is fiberglass there is a strong possibility that a sealer will need to be applied. I had the hood on my Ranger Edge replace last year and the painter figured that he would sand, primer and paint over what Ford had applied at the factory. After a few failed attempts he called his paint supplier and he told him that he needed a primer sealer for use over fiberglass.

 

Could also be the type of paint it was repainted with.

 

Nope. Sanding between coats hasn't been a thing since laquer paint. Color sand your clear and you have a smooth a finish as you are going to get.

 

I only wet-sanded in between primer coats and in between the base and clear coats. The clear did have trouble adhering as it was peeling after a couple months. I could have just applied it wrong too.

 

I just ordered 3 cans of black primer, 3 cans of Black sand pearl basecoat, 2 cans of clear coat and a spray can handle sprayer. Going to attempt to paint my fender flares. I'm also going to paint my rock sliders prior to having them weld them on. They'll get a little love but I'm not going to go too crazy cause they're only gonna get banged up anyway!

Thanks!

 

You got this. Make sure to sand any imperfections.

 

Yep bought a bunch of different grit sandpaper also!

 

Don't be afraid to use bondo if you need it!

 

My passenger rear quarter fender flare looks like it took a slight impact of a right turn not well thought out from the previous owner. Its not too too bad but I might try to bondo/prime/paint it or find another in good shape from Rancho recycling.

 

Try NNAWG Reno Airport. My flare was $20

 

Thanks! I'll check em out.

 

Every 2 stage paint has a window of time to get the first coat of base down.

If you miss the window you get all kinds of adhesion issues. Dodge had a long run that they screwed that up on their trucks and almost every truck on the road was losing its clear on the hoods and fender edges. I think the paint was fine but poorly applied. We would see the same whenever a big hail storm came through and a bunch of vehicles would get fresh paint. The only fix for bad timing is let the base harden and wet sand but that tales more time than a shop is willing to put in.. The best method though is make sure you make the window, no sanding needed.

Doing a real mirror finish takes a lot of color sanding and polishing. The extra clear coats were there so you didnt sand down to the color coat. Back in the day when we had cassette tapes I used one as my test. When i could read the small print in the paint, I was done. Several hours per panel to get there though. I don't have fancy cars, what I do have isn't worth that kind of time. No one sees orange peel at 80mph