How to Prepare Old Metal for Painting

Notice all the popped up metal and pitting on this

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By can-do
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Maybe you have some rusted, pitted or worn steel lawn furniture you want to preserve and repaint. Possibly pot metal trim on a car is worn, faded and pitted. Maybe the outdoor electrical box cover has rusted and needs a face lift, or maybe the hand rail leading up the stairs in front of your home that is 50 years old and been repainted 20 times needs a new life! In any event, you can save that metal and make it look and feel new again. Rather than tossing it or just painting over and over the old caked up paint, why not do it right!

Difficulty: Moderately Easy

Instructions

Things You'll Need:

Dremmel tool with grinder attachment or any small grinder
Sandpaper (60-120-320 grit)
Safety glasses if you will be grinding (snug to face style)
Heavy work gloves if you will be grinding
High build automotive primer
Automotive spot glazing compound, if metal is flawed
Liquid metal filler may be needed depending on severity of damage for filling holes and scars
Hair dryer (Optional)
Paint remover, if you are working on already painted metal

Step 1

Take a survey of the metal to determine what tools your may need to get it smooth, which is the object here. Anytime there are holes or pitting where the metal has popped up, rust, or sharp cuts or edges you will need the small grinding tool. A dremmel tool with the grinder attachment really works well for this.
Step 2

If you are working on metal that has already been painted, you should first work with paint remover, following label instructions before moving to the next step.
Step 3

Dremel Tool with small grinder attachment, perfect for small areas and contours.

If the metal requires grinding as mentioned above, wear safety glasses and gloves before using the grinder. Grind below any pits or rust, remove sharp edges and grind any scars or scratches as smooth as possible. Keep the grinder moving and work it in a way to get a level surface in the bad area. Don't hold it still for very long in the same spot or you will distort the metal and create a valley or dips in the metal. You do not need to grind the entire piece, just the bad spots.
Step 4

If grinding was necessary, use 60-grit sand paper and sand your grinding marks down for a smoother surface and to sand below any rust to bare metal missed with the grinder. Then follow up with 120-grit paper for a yet smoother finish and also to remove any surface paint or dull the chrome, if this happens to be the finish.
If you did not grind, just move right into sanding with 60-grit and over to 120-grit. The goal you are after is a smooth dull finish.
Step 5

Liquid metal and 60 grit paper for sanding it down.

If you have any indentations or holes from rust in the metal you can use the liquid metal to fill in these spots. Press the compound into the openings and don't worry if the surface is not flush with the metal, you will sand it smooth later.
Step 6

Glazing spot putty compound and 120 grit paper for sanding it down.

For smaller surface imperfections you can apply your spot glazing compound, keeping in mind that this product is only meant to be layed on up to 1/16 inch or so.
Step 7

After your product has dried you can sand with the 120-grit paper to obtain a smooth surface. The liquid metal may not be sandable for a number of hours and may require the 60-grit paper to bring smooth, but the glazing compound should be ready to sand within 30 minutes or so, depending on humidity and temperature, with 120-grit.
Step 8

High Build automotive primer applied.

Now spray on 2 to 3 coats of the high build primer, letting dry between each coat. A hairdryer works nicely to speed up the drying process between coats.
Step 9

Glazing spot putty compound applied, ready for sanding smooth.

Look closely now into the primer for any remaining imperfections such as low spots. Use various types of lighting if possible to help identify imperfections. Glaze with the spot putty any remaining flaws, wait to dry, and sand smooth with 120-grit.
Step 10

Finished Product!

If you re glazed any spots, you will need to apply a spot coat or two of primer to the area. Final step is to "lightly" sand the entire piece with your 320 grit sandpaper, just to obtain a very smooth finish. You are now ready for your finish paint and maybe some clear coat for added protection!