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With Chris Curwen & Expert Auto Painter - Dave Gage (Car Cosmetics)

June 5th, 2007 - Issue 06

In this issue:

• We continue along on the subject of Surface Preparation and this week we'll discuss Paint & Rust Removal.

The amount of old paint that you are going to have to remove depends on the current condition of the paint, whether or not the vehicle requires any bodywork (we will cover bodywork in future issues) and how far-reaching your paint job will need to be.

You can apply new paint over old paint once the existing finish has been sanded so that all oxidized paint material has been removed and you've left yourself with a smooth, flat and even surface.

In addition, you don't want to apply new paint over anything that is lacquer based. If the original paint is lacquer based, then you will need to sand the areas to be painted down to bare metal.

You will then need to use an undercoat that is compatible with the top coat you plan to use. This is to ensure you don't suffer any complications in getting the new paint to stick.

For any vehicle that needs bodywork doing to it, you'll need to take the repair area down to bare metal so that the filler material has the best chance of bonding properly.

A professional demonstration of paint being removed from the repair area of a car down to the bare metal is shown in 'How to Paint a Car - The System' - Part 2.

The decision to paint is made simple if your vehicle needs bodywork or it has serious paint imperfections.

If the old paint looks dull or oxidized however and you wish to repaint it to make it look visually appealing once again, ask yourself these questions:

* Is the paint currently on the vehicle too thick to support a new finish?
* Does the body suffer from rust anywhere?
* Will you need to paint the entire vehicle or just some of the panels in order to finish the job?

You will need to decide how much painting your vehicle is going to actually need. If you're not sure how much simply ask at your nearest auto paint and supply store for their opinion or at a local body shop.

The best way to remove paint is decided by the condition of the vehicle's current paint surface.

You should really use only the mildest methods such as chemical stripping on cars with bodies in excellent condition that require no sheet metal repair.

If however the paint on your vehicle is significantly cracked, peeling, bubbling or flaking, you are much better off stripping it down to bare metal.

If the current paint on the car is not adhering properly, whatever paint you put on top of it will not adhere properly either.

Stripping paint is done by either of the following three methods:

* Sanding
* Media Blasting
* Chemical Stripping/Dipping

Sanding

It is a good idea to purchase a stripping disc kit that has stripping discs and a cushioned backing pad. This will attach to an angle sander (a buffer) with high speeds of up to 6,000 rpm.

They will strip the paint quickly and effectively without generating excessive heat and due to their design, they won't damage body panels.

They are recommended for use after a chemical stripper has been used to remove most of the old paint however this isn't compulsory. From previous, you will find a variety of chemical strippers at your local auto body paint and supply store.

A high speed rotary sander with a coarse disc will remove paint quickly. These are perfect prior to bodywork because they leave rough sanding scratches on the surface, excellent for filler to bond to.

A high speed sander and a coarse disc will also do an excellent job of removing rust.

Remember that high power sanding tools will generate a lot of heat. If the tool remains in one location for too long then the friction can cause enough heat to warp the surface. The risk is higher on newer model vehicles because of their thinner panels.

Remember: DO NOT TRY TO SAND ALL THE PAINT OFF YOUR CAR WITH A ROTARY SANDER OF ANY TYPE.

Media Blasting

Sand blasting, also referred to as media blasting, is another great way to remove old paint quickly from a vehicle, especially those hard to reach places.

This method also works very well on older model vehicles with cases of surface rust. There'll be a lot to clean up after you blast but it will be well worth the effort.

A sand blaster works by combining pressure with a compatible media. Be careful not to apply too much pressure with the harsh media otherwise the sheet metal will warp along with other damage.

To be safe, remove all of the exposed accessories and body parts from the vehicle; the process of sand blasting will take off chrome as well as paint and deface glass.

You can learn more about the proper type of media and pressure you should use for the various types of jobs by referring to 'How to Paint a Car - The Written Guide'.

Chemical Stripping or Dipping?

If you wish to start with clean metal before you begin the repainting process, using a chemical stripper would be ideal.

The chemical stripping process will remove all of the layers of primer, paint, wax, grease, dirt and anything else that can be found on the vehicle.

After the stripping process is done you'll have a shiny, bare metal surface to work with.

One drawback of dipping a metal body or component is that the rust removal agent will get into all of the minute surface areas; exposing them to the environment.

Try to access all these areas and apply epoxy primer. This is a very successful way to eliminate rust.

Unless you are dipping only a single layer of sheet metal, then you won't be able to apply epoxy primer to all of the bare surfaces.

It won't pose a problem in a dry climate however, in a humid climate; rust will surely form on the areas of bare metal that are left untreated.

Always use the proper safety equipment when you are using any kind of paint stripper. This includes a respirator and gloves. After all, if these products are potent enough to remove paint, just think of what they can do to your body.

To discover what you must use to scuff the panel with prior to applying stripper and why this is important please refer to 'How to Paint a Car - The Written Guide'.

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That's all we have for you this week. Thank you very much for reading. We both hope this issue has been of valued interest to you.

Next week we'll continue with Surface Prep and move onto Applying Primer Material.

Happy Painting!

Chris Curwen & Dave Gage
www.LearnAutoPainting.com