Primer, sanding, repeat...advice please

[Caleb Provencio]

I've got some spots on some rims and fenders that aren't bad enough for bondo so I was planning on using a building or filler primer on them. I was planning on spraying on the primer, sanding and doing this as many times as needed to cover the scratches and small imperfections. Here are my questions:

1. After I sand the primer, how do I make sure I've got all the dust off before starting with my second coat of primer? Seems like just wiping off with a rag or using the air compressor to blow them off isn't going to get it all off. Wet rag and completely dry before second coat? Alcohol wipes?

2. What is the difference between etching primer and filler primer? The shop I got my paint from gave me etching primer. Should I use this first then come on top of that with my filler primer?

Thanks in advance for the help and advice.

Caleb


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[Duchess]

1. Most people use tack cloths, but I use microfiber rags and alcohol.

2. Etching primer has an acid to cut into the base material. For aluminum, this is pretty much a must because the metal picks up a fine layer of oxidation very quickly (this layer retards further corrosion), which makes bonding difficult and the acid eats into it. You still want to clean off the top layer and paint ASAP. Filler primer is thicker to fill minor imperfections.

 

[Fv2]

1. Most people use tack cloths, but I use microfiber rags and alcohol.

2. Etching primer has an acid to cut into the base material. For aluminum, this is pretty much a must because the metal picks up a fine layer of oxidation very quickly (this layer retards further corrosion), which makes bonding difficult and the acid eats into it. You still want to clean off the top layer and paint ASAP. Filler primer is thicker to fill minor imperfections.

Yup
I'm one of those who use tack cloth, I'd say etching primer is a good idea if painting over chrome too.

 

[us56456712]

I've got some spots on some rims and fenders that aren't bad enough for bondo so I was planning on using a building or filler primer on them. I was planning on spraying on the primer, sanding and doing this as many times as needed to cover the scratches and small imperfections. Here are my questions:

1. After I sand the primer, how do I make sure I've got all the dust off before starting with my second coat of primer? Seems like just wiping off with a rag or using the air compressor to blow them off isn't going to get it all off. Wet rag and completely dry before second coat? Alcohol wipes?

2. What is the difference between etching primer and filler primer? The shop I got my paint from gave me etching primer. Should I use this first then come on top of that with my filler primer?

Thanks in advance for the help and advice.

Caleb


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Clean with a solvent, use metal etching primer; many thin coats, then Bondo scratch filler, wet sand with 400 grit and use many coats of regular primer. Avoid filler primer in a rattle can as it just gums up in the nozzle. Allow 10 or 15 minutes between coats of regular primer. Avoid drips with thin coats. Fine sand and top coat. I typically use one can of metal etching primer in thin coats and two cans of regular primer in thin coats before top coat on a bike frame. If you do this and fill any glaring spots with scratch filler you don't even have to strip the frame to bare metal. This much primer can cover a multitude of chips, scratches and other bad stuff without stripping off the old paint.
First I dipped the frame in weak phosphoric acid but white vinegar works as well.

Came out of the acid looking like this.

Two and a half cans of primer and a half can of blue under coat.

One half can of metal flake blue top coat.

Another bike I did the same to except it already had a blue rattel can paint job with many drips. I sanded out the drips and did the same treatment to it as the tandem, no paint stripping
I clear coat with 2 part rattle can paint. I use Spray Max 2k High-Gloss Clearcoat aerosol.

 

[Duchess]

Did not know there was 2k rattle can clear! Is it more durable than the snack-worthy 1k clear that chips at an angry look (OK, I'm exaggerating how bad it is, but it's definitely not great)?

 

[us56456712]

Did not know there was 2k rattle can clear! Is it more durable than the snack-worthy 1k clear that chips at an angry look (OK, I'm exaggerating how bad it is, but it's definitely not great)?

It't rock hard. I dropped my tandem frame from head height onto a concrete floor (the rope holding it slipped out of my hands when removing the frame from its tie down on my garage truss) and it put a small scratch in it. The problem is it's highly toxic to the lungs when spraying. I bought a tyvek hooded full sleeved paint suit, industrial quality respirator, and eye protection. I used rubber swamper boots and 2 pair of nitrile gloves. I painted it outside on a clam day as I didn't want any fumes getting into the house from the garage. You can make a paint booth out of inexpensive vinyl sheets (from the building materials supplier) or probably plastic tarps. I use free wood pallets and/or cardboard to make a 3 sided topless windscreen paint booth. It looks like a homeless shelter. It dries really fast and has an awesome spray nozzle as good as my spray gun and compressor. Works great.
http://www.spraymax.com/index.php?id=361&L=1

 

[Duchess]

Thanks. Yeah, I painted my road bike with automotive paint. I don't have a compressor, but the base coat went on perfect and easy with Preval sprayers. The clear coat did not. Ended up wet sanding it off and having it done correctly at an autobody shop. I use a full-face gas mask and cover the skin (and still try to keep breathing to a minimum). I shot in my garage but, yeah, the clear coat seemed even nastier than the base for fumes. I think you've got the better idea with the shelter. Rattle cans didn't seem nearly as bad or lingering.

 

[us56456712]

Thanks. Yeah, I painted my road bike with automotive paint. I don't have a compressor, but the base coat went on perfect and easy with Preval sprayers. The clear coat did not. Ended up wet sanding it off and having it done correctly at an autobody shop. I use a full-face gas mask and cover the skin (and still try to keep breathing to a minimum). I shot in my garage but, yeah, the clear coat seemed even nastier than the base for fumes. I think you've got the better idea with the shelter. Rattle cans didn't seem nearly as bad or lingering.

My friend does auto body and paint. He mentioned that some of the new clear coat is very hard to apply correctly, you have to go to a paint school put on by the manufacturer to learn to do it right. Just make sure you follow the directions and shake it vigorously. I recall they recommend a 2 minute shake, then release the catalyst and then shake again, I think for another minute. I think you have to stop spraying every 15 seconds and agitate again, but I am trying to remember this so I am not sure but it is something like this. point being that it is important to really follow the directions.

 

[Caleb Provencio]

I'll have to see what kind of clear coat they gave me at the auto shop. I know they said that once I spray my flat clear coat the can has to be used within 48 hours or something like that. I'll have to call them back and make sure a novice can spray the flat clear coat (I'm doing rat rod flat black frame with bright red rims). Thanks for letting me know some can be hard to get on.

Also, I'm going to take your advice and build a spray booth out of clear plastic tarps out on the side yard. Great ideas!


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[olddude13]

Spray max looks interesting. I use auto type clear with catalyst a quart goes along way on bike parts I think spray cans can get expensive! i use a gravity gun from lowes.
Just my two cents

 

[Indyjps]

I'm not a pro painter by trade but have been restoring cars and doing bodywork for years. IM if you want to discuss paint. I end up with a lot of cans of paint with 1/4 inch in the bottom, just enough for a bike.

Acrylic enamel, acrylic urethane are what you'll find for most auto paints, both can be base coat, clear coat, or single stage (1 coat). Lacquer is also available.

Rustoleum, Valspar etc is not automotive paint, it's an oil base enamel. Using a mix if 7 parts paint, 2 parts acetone, 1/2 part valspar enamel hardener it creates a good paint job, I shoot it a lot on equipment. The hardener makes all the difference, but the hardener is what's toxic, so buy a respirator.
This paint is probably as good or better than what vintage bikes got originally.
The issue with clear coat over this paint is its oil based, the solvents in automotive clear coat lift it. Many rattle can clears are lacquer, again incompatible solvents. This is best for single colors.

I'm doing some test samples of valspar thinned with acetone as above. Letting it out gas and cure for long times, then seeing if I can get cheap cheap automotive enamel clear vs. Mid level auto clear to go over it without lifting. I'll use different reducers in the clear to see how they'll react. I'm just curious if it will work and it's a common topic on some auto websites I go on. I have a feeling the cheap cheap clear is closer to an industrial product and may be more forgiving. Point is, if it works, I can lay pearl over rustoleum.

If you want to get into auto paints, finding somwehere to sell small qty is expensive. Stick with 1 brand and 1 type, urethane/enamel so your solvents transfer. I've considered talking to my local PPG paint supply about running me 4-5 pints of various colors, but not specific colors red blue white etc to see if they can cut me a good price. Then I can mix pearl or flake into the clear.

Harbor freight paint guns. Some love or hate them. It'll never be a $500 gun, but I don't think we need perfect paint atomization to shoot a tube frame bike. It's different laying paint on a large flat panel. I have expensive paint guns, but reach for the HF gun quite a bit for small stuff.

Tcp global, summit, kirker, paintforcars, PPG shopline or delfleet, transtar, even NAPA, all offer budget auto paint lines that will exceed the paint most bikes came with. Powder coat is an option, but I prefer to shoot paint on cars and bikes.

 

[franconuevo]

I've found that whether you are taking the frame down to bare metal, or just sanding the existing paint down for a color change, there's always fine scratches & imperfections...so IF I'm going to paint a frame..or a fork, I prime with filler primer. I haven't had a problem with it gumming up the tip. Always have good luck with this primer from Horrible Freight:

Usually I'll use whatever paint I have in the shed at the time...could be Valspar or Rustoleum or Ace...The biggest problem with rattle can paint is over-spray, and it doesn't matter if I'm on the lee side of the house, or in the shed. But, it's no biggie..you don't really have to go at over-spray that hard, I usually just smooth it between 'light' coats with a scotchbrite pad.
Valspar is good because it dries fast..Rustoleum..not so much.
Rustoleum seems more durable by far though after it cures.
Here's a bike I painted with Valspar..polish and wax...nice finish.

If you want a black satin that works use Ace Enamel...big can, and it seems to really lay the color down.

I don't usually clear coat, because it always seems to wrinkle the paint job, somewhere..no matter if I use all the same brand, don't use lacquer over enamel, etc. I usually just let the paint cure...not dry..cure, and then polish and wax.
However , I'm doing a two color fade (Valspar paint) on an old beat mountain bike right now that someone gave to me...and clear coating that. I'm using it as a test bike so to speak for trying different painting techniques. When I'm done I'll just sell it on C List. So, I've found that using light light coats , letting it tack up (15 minutes) in between seems to be working ok. I must have just been trying to lay clear on too heavy in some of my attempts.
Rustoleum over Valspar..working fine.

My favorite however is...tada...Duplicolor Engine Enamel over harbor freight filler primer , I used it on the Muscle bike I did for the build off...stuff goes on like glass

That's all I know..today anyway.

franco

 

[LukeTheJoker]

Duplicolor seems to be a good choice for most of us!

 

[fjernt]

Pure gold this, ty vm indy, and thanks for bumping it luke

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