I'm doing a repaint of my vehicle that is currently red. For the panels and areas that don't require any bodywork, if I sand the existing clearcoat with P400, is it ok to paint black basecoat over it or will the red bleed through? Thanks!

it should be black, but I think I would use a sealer were you dealing with different substrates. not necessarily for color with black but for adhesion also.
Jay D.

A quality base coat will adhere to a sound substrate sanded with P800 for metallics orP600 for solids. P400 is a little coarse and you run the risk of sanding scratches showing through.

Sealers are nice, but not really essential unless the substrate is incompatible with the base coat. Really the only common instance of this is where a thermoplastic acrylic has been used and this is only on plastic panels. Other doubtful substrates like enamels or damaged paint should be removed. Rub throughs need to be primed to cover any exposed layers in the feathered edges.

For a quality base coat two coats should cover your red while for an economy base coat you may need three coats. Do some spray out cards first to check what you need.

The situation may be different if you were painting yellow, white or red over a different colour substrate because these colours tend to be very transparent. Black isn't.

EllieMae94 wrote:I'm doing a repaint of my vehicle that is currently red. For the panels and areas that don't require any bodywork, if I sand the existing clearcoat with P400, is it ok to paint black basecoat over it or will the red bleed through? Thanks!

As stated above if the existing clear coat is in good condition you should be fine. I also agree that P600 is a much better choice for solid colors than the P400.

If it were me, I would use a reduced epoxy for a sealer coat. This will reveal if you have any incompatible materials on there and if not it will lock down what is below and provide a consistent color to paint over.

Depending on the quality of the paint you are using and your technique, full coverage is generally produced with 3 coats. A pro with high end materials will get that in 2 coats but I like to err on the side of caution and apply 3 coats of base with dark colors.

NFT5 wrote:A quality base coat will adhere to a sound substrate sanded with P800 for metallics orP600 for solids. P400 is a little coarse and you run the risk of sanding scratches showing through.

Sealers are nice, but not really essential unless the substrate is incompatible with the base coat. Really the only common instance of this is where a thermoplastic acrylic has been used and this is only on plastic panels. Other doubtful substrates like enamels or damaged paint should be removed. Rub throughs need to be primed to cover any exposed layers in the feathered edges.

For a quality base coat two coats should cover your red while for an economy base coat you may need three coats. Do some spray out cards first to check what you need.

The situation may be different if you were painting yellow, white or red over a different colour substrate because these colours tend to be very transparent. Black isn't.

Thanks, guys for taking the time to respond. These responses have led to a few more questions I have.

First, I need to expand a bit on my situation. This truck that I am repainting black was painted a year ago by yours truly. The original factory OEM paint was white (basecoat/clearcoat). I fixed the minor dings and small rust issues last year. Areas that were sanded to bare metal were primed with Tamco's 2K High Build. The areas on each panel that was in good shape I sanded the clearcoat with P400 wet. Then shot basecoat/clearcoat. No issues with any of that. Basecoat/clearcoat that was used was Omni. Now I want to fix a few areas and this time I am doing another color change to black and am using Tamcos Jet Black basecoat and clearcoat. Since I have a lot of areas with several layers of paint (factory primer, basecoat, clearcoat, Tamco primer, Omni basecoat/clearcoat, I'm thinking I need to at least sand the previous basecoat/clearcoat I shot last year. Would this be a wise move?

When you mention rub throughs need to be primed are you referring to areas where I rub through to metal, or areas where I broke through the clear? Then again, this might all be a moot point if it would be better to sand the existing base/clear and then shoot fresh primer, followed by base/clear?

Hope I made sense, thanks again to everyone for all their help and advice.

'68 Coronet R/T wrote:

EllieMae94 wrote:I'm doing a repaint of my vehicle that is currently red. For the panels and areas that don't require any bodywork, if I sand the existing clearcoat with P400, is it ok to paint black basecoat over it or will the red bleed through? Thanks!

As stated above if the existing clear coat is in good condition you should be fine. I also agree that P600 is a much better choice for solid colors than the P400.

If it were me, I would use a reduced epoxy for a sealer coat. This will reveal if you have any incompatible materials on there and if not it will lock down what is below and provide a consistent color to paint over.

Depending on the quality of the paint you are using and your technique, full coverage is generally produced with 3 coats. A pro with high end materials will get that in 2 coats but I like to err on the side of caution and apply 3 coats of base with dark colors.

Thanks Coronet. I hope you have found my response posted above that clarifies my situation. If I have an incompatible material, would what the effect be? Is this in reference to "lifting?"

With that many layers of paint you will want to sand it.

Everything you mentioned should be compatible however exposed base that wasn't activated could lift on you. By shooting reduced epoxy for a sealer these may lift but at least you have a chance to correct the problem without wasting any of your new paint. If the sealer lays down fine you are good to go.

EllieMae94 wrote:When you mention rub throughs need to be primed are you referring to areas where I rub through to metal, or areas where I broke through the clear?

Both. In either case the feathered edges are where you risk frying up.

EllieMae94 wrote:I'm thinking I need to at least sand the previous basecoat/clearcoat I shot last year. Would this be a wise move?

Yes, as Coronet said.

I just had a quick look at Tamco's web site. Their primer range is impressive but importantly they have both DTM primers and epoxy primers in black (as well as white and grey). Using the black primer all over will likely save you some money in base coat.

'68 Coronet R/T wrote:With that many layers of paint you will want to sand it.

Everything you mentioned should be compatible however exposed base that wasn't activated could lift on you. By shooting reduced epoxy for a sealer these may lift but at least you have a chance to correct the problem without wasting any of your new paint. If the sealer lays down fine you are good to go.

I forgot to mention that in my last post. The Omni base that I shot last year was not activated. Sounding more like I need to do it "right" and strip all the layers of paint and start fresh.

Very good. I attempted to sand off the layers of paint on the tailgate until hitting the primer I laid down last year or the factory OEM paint with bad results; it was too easy to sand past all of that so I decided to strip the entire panel down to bare metal. It went rather quickly using those 3M stripping disks and finishing it off with 80 grit on a DA.

In regards to a sealer primer, one of the reasons why I purchased Tamco's DTM 2k primer is because it states it can be reduced to use as a sealer. Would this be at least equal to using a reduced epoxy primer for sealing? Does the epoxy have better properties for adhesion?