Aluminum alloy is durable, lightweight, and it has good corrosion resistance to atmospheres. Therefore, aluminum alloy is commonly used in everyday life, especially in the Furniture/Home Furnishings industry. To embellish and protect the surface of the cast aluminum, the painting aluminum process must be carried out.
The cast aluminum alloy has a much smoother surface than other metals, so it is not easy to perform the painting cast aluminum process. Besides, cast aluminum is nonporous, so it does not accept paint as well as wood materials. If the paint is not applied correctly, after a period of use, it will be rubbed off and formed paint blistering.
Why is it necessary to paint cast aluminum alloys?
- Colored aluminum alloy does not refer to the furniture’s aesthetic value but the painting does.
- While aluminum itself is corrosion resistant, the elements of its alloys are not, so aluminum alloys oxidation can still be possible. Therefore, the appropriate coating will prevent oxygen from reaching the metal underneath and help resist corrosion.
Painting cast aluminum selection
Choosing the appropriate paint is a crucial part, especially the primer. Primer conceals the defects of cast aluminum, etches on the aluminum surface, and helps increase adhesion to the main coating.
Previously, the zinc chromate-based primer was widely used for its performance, but it is no longer popular because of health and environmental concerns.
Today, Zinc-based Primer or Zinc Rich Primer is one of the most effective primers used to paint aluminum. It is a special oil-based paint that is used to prevent metal surfaces from rust and as a primer for high-end painting systems.
Not only can zinc-based primers create a barrier between the air and aluminum, but they also use zinc’s chemical properties to shield aluminum. The zinc content in the primer is highly sacrificial anodic. High-concentration of zinc dust provides cathodic protection properties as it reaches metals.
There are two types of zinc based primers, organic and inorganic.
- The organic primer is usually used with brushes, roller, or spray. It will not protect the surface as well as an inorganic primer. Therefore, it is a must to cover it with a topcoat.
- The inorganic type is mostly used only by spraying. It provides better surface protection than organic paint without the need for a topcoat.
You can choose from either one of the two. However, adding a topcoat to optimize the aluminum surface protection is recommended.
You can use any oil-based paint as a topcoat in the color that suits your preference. Oil-based paint will adhere to the primer better and make it harder to come off.
Painting cast aluminum process
We have produced a safe and effective coating for aluminum alloys process by researching the properties of aluminum materials and their alloys.
Step 1: Cleaning the surface
Preparing aluminum surface for painting is important! Ensuring the surface of aluminum objects to be painted is clean, not greasy, and dustless by using brushes and cleaning chemicals.
Aluminum is durable, so you can absolutely use hard brushes to remove stains. Then rinse with water, pat dry and let it sit for 2 hours.
Step 2: Shielding
Before painting cast aluminum, you must cover the unwanted parts with tape or paper. Place the object you want to paint on the small canvas.
Step 3 : Painting the primer
After deciding which zinc-based primer to use, prime the surface of the aluminum casting.
If you choose organic paint, use a brush or roller to paint over the surface. If you use the inorganic paint, spray it at a distance of 6-8 inches.
Applying too much can cause paint drips. Wait about 4 hours before applying the topcoat.
This primer painting will etch onto the aluminum surface to create abrasion which makes it easier to adhere top coat.
Step 4 : Painting the topcoat
Use a paint roller to paint on the surface of the casting. Using white paint before conduct other color painting is recommended.
After the paint dries, you can apply a second coat on the surface and wait 24 hours before touching the object.
Other painting cast aluminum options
In addition to using zinc-based primers as mentioned above, you can also use galvanized metal self-etching spray primer. It is a spray-coated galvanized paint that is just as effective.
With spray paint, spray at a distance of 8 inches, and be sure to wear a face mask to prevent harmful odors. Wait about 4 hours and then paint Acrylic Enamel on the object’s surface.
Acrylic Enamel Paint is a specialized water-based paint used in car painting, despite the effectiveness is not as good as oil-based paint, this paint will save money and effort.
Also, there are several specialized aluminum paints on the market; nevertheless, these can create a layer of aluminum oxide on the object’s surface, which will make it difficult for your interior to cling on. If you choose to use these kinds of paint, you must cover the surface with a primer coating at the beginning of the process to ensure effectiveness.
Thus, VIC has instructed readers on how to paint the surface of cast aluminum objects effectively. However, be noted that no paint can last forever.
Metals were not made to be cover with color liquid; therefore, the paint will flake off after a few years of use. You should repaint it when there are signs of peeling off.