Because of its smooth, even surface, galvanized steel is difficult to paint. Before starting painting, the smooth surface of the steel must be treated so that the paint can adhere to it. First, wipe the steel with a chemical degreaser. Then etch the steel with white vinegar so that the paint can stick to it. Remember to rub down the old steel with a fine-grained sandpaper to remove any traces of oxidized zinc (or "white" rust). Finally, apply a general purpose outdoor latex primer to the surface, then finish painting with two even coats of quality outdoor latex paint.
Part 1 of 2: Prepare the surface
Step 1. Treat steel with a chemical degreaser
Spray the surface of the steel with this product, then wipe it with a clean, lint-free cloth. A powerful degreaser, it will corrode dirt, grease, mold and other problem marks without affecting the capricious zinc coating. Brush the surface in small sections until the entire surface of the steel is ready.
- You can use household products such as Comet, white spirit and chlorine bleach to prepare galvanized steel for painting.
- If you want to paint side panels, roof waterproofing joints or other materials that have been exposed to water, air and sun, they must be thoroughly cleaned first to remove organic contaminants from the metal surface.
Step 2. Wait for the steel to dry
After cleaning the steel, wait until all traces of degreasing agent have evaporated. This way you don't have to worry about the product coming into contact with the vinegar while etching the smooth steel surface.
If possible, carry out all preparatory and painting work indoors or on a clear day with low humidity
Step 3. Wipe down old galvanized steel to remove white rust
When working with a worn product, you may notice a chalk-white and powdery film on some areas of the steel. With a little patience, it can be easily sanded with fine-grained sandpaper (120 grit or less). Sand the steel with gentle circular motions until the surface is smooth.
- Wipe the surface of the steel with a cloth dampened in warm water to remove dust.
- This white substance is called "white" rust. It appears when a thin layer of galvanized steel begins to deteriorate over time or due to exposure to water, air and sun.
Step 4. Wipe the steel with white vinegar
Soak a clean, dry cloth in distilled vinegar and then wring it out. Walk thoroughly over the galvanized steel, periodically dampening a rag with vinegar. In order for the painting to be uniform, it must lie on the entire surface of the product.
- The acid in the vinegar will etch the smooth galvanized finish, giving it a rougher texture that will allow the paint to adhere better.
- If you miss a spot, the paint may stain or flake off.
Step 5. Leave the product for 1-2 hours
During this time, the bite should have time to etch the galvanized surface. The more time passes, the more pronounced the etching effect will be and the better the paint will adhere. If you are not in a hurry, leave the product on overnight.
If you are short on time, wait for the surface to dry before proceeding to primer and paint
Part 2 of 2: Apply a primer and paint the steel
Step 1. Apply latex primer
Spray the prepared steel surface with a primer or apply with a brush. Apply the primer in small sections to ensure an even layer. There should be no gaps or thin layers of primer on the surface, which will cause problems during subsequent painting.
- For maximum strength and durability, use a versatile outdoor latex primer.
- If the steel product will be exposed to harsh industrial environments or outdoors, buy a better quality epoxy primer. Epoxy primer is more durable and resistant to scratches, chipping and flaking.
Step 2. Wait until the primer is completely dry
Depending on the primer used, this can take from 2 to 6 hours. To check if the surface is ready for painting, slide your finger over it. If the surface is still sticky, then it is not completely dry yet.
Do not apply paint on wet primer as it will not adhere well
Step 3. Choose a suitable paint
Generally, regular outdoor latex paint is suitable for most projects. It can be easily found at a hardware store or hardware store. Do not apply alkyd paint (such as spray paint) to galvanized steel.
- Instead, find a paint that is specifically designed to be applied to galvanized steel.
- The enamel in alkyd paint can react with the smooth finish on galvanized steel and cause poor adhesion and flaking of the paint.
Step 4. Apply the first coat of paint with a brush
Apply paint in long, straight strokes. Use the tip of the brush to paint all grooves, crevices and embossed places. Make sure you haven't missed anything before proceeding.
It is very convenient to use a roller to apply paint to wide surfaces such as side panels or lid panels
Step 5. Wait for the base coat to dry
It should take about 3-4 hours before applying the second coat. In the meantime, do not touch fresh paint. Otherwise, streaks or folds will remain on the finished finish.
In warm and humid weather, the paint will take longer to dry
Step 6. Apply the second and final coat
Two coats of paint are usually sufficient for most projects. Apply the top coat like the first. Take your time and make sure the top coat is evenly applied. Imperfections can appear after the paint has dried.
- Indirect airflow from a fan or air conditioner will allow the top coat to dry faster.
- When the top layer is dry, install the product or start using it.
Step 7. Do not expose the product to wear while the paint dries
While most latex paints dry in a matter of hours, it can take several weeks (and sometimes a month) to fully cure. Avoid exposing steel to wear or heavy stress, precipitation or sudden temperature fluctuations whenever possible. Once dry, the paint will be ready for whatever wear and tear it has to endure.
Done correctly, galvanized steel paint will last longer and be more resistant to extreme conditions
- Wear a pair of disposable rubber gloves to keep chemical cleaners and latex paints out of your hands while you work.
- Painting galvanized steel is a quick and inexpensive project that anyone can do. All you need is a little paint, a primer and a few hours of labor, most of which will take the paint and primer to dry.
- The surface of galvanized steel is sometimes treated with a passivator, which protects the exterior from corrosion, but can complicate painting. To check, sand an inconspicuous spot on the finish and wipe it and the surrounding surface with copper sulfate diluted with water. If the steel darkens at different rates, then it was most likely treated with a passivator and therefore you will not be able to paint it without first leaching.