- 21 December 2024
Aluminum has many useful properties - it does not rust, does not require special care, and due to its light weight it can be used where weight reduction is necessary without sacrificing performance and strength. However, the metal also has disadvantages that reduce its versatility. The main disadvantage is that water-based paints do not adhere well to aluminum, complicating its painting with conventional means.
A thin oxide layer forms on the surface of aluminum. Chemically, the metal atoms on the surface come into contact with oxygen. This leads to the formation of metal oxide, which remains on the surface of the metal in the form of a thin layer. At first it may seem that this film is harmful, since it reduces the strength of the material. However, this is not the case - the film not only does not reduce the strength, but also performs a number of useful functions. The main one is that the oxide layer prevents the metal from coming into contact with atmospheric liquids and gases. This improves the anti-corrosion properties of the metal, which positively affects its strength, reliability, flexibility, durability and other parameters. At the same time, it is this layer that makes it difficult to paint aluminum. A thick layer of oxide provides stronger protection for aluminum parts against environmental influences. Therefore, ordinary water-based paints adhere to aluminum less well (compared to other metals and alloys). Painting aluminum with ordinary paint is practically pointless. Of course, such paint will adhere to the aluminum surface and harden. However, over time it will begin to crack and peel. The rate of peeling is influenced by the shape of the part - simple, homogeneous parts hold paint a little longer than parts with complex shapes.
However, there is a way out of this difficult situation - powder coating of aluminum. Powder coating of aluminum has its advantages - it allows additional protection of the metal surface and a decorative finish. Before using paint for aluminum, it is necessary to clean the surface of the part to be painted, because if there are a large number of bumps, the adhesion of the powder to the metal surface is reduced. Clean the surfaces of all roughness, scratches, dents. Sandpaper can be used to clean the part. Keep in mind that the oxide layer is removed during processing, so the metal surface should also be degreased.
Powder coating of aluminum is effective because of the composition of this type of paint. Organic polymers usually act as film-forming agents. They form a thin, uniform layer on the surface of the metal, which evenly covers the aluminum. Usually the film-forming substance is colorless and performs several tasks. The main one is to protect the metal from exposure to external aggressive environments. The second important function is to form a viscous, uniform layer to which the coloring ingredients safely adhere. Membrane-forming substances are produced on the basis of thermoplastic or thermosetting polymers.
These aluminum paints also contain a coloring pigment. Compounds of organic and inorganic origin can be used as pigments. Almost all color pigments are suitable for powder coatings. Therefore, powder paint can be any color - black, white, purple, blue, green, light blue, ruby.
It is also possible to spray paint aluminum, which can be done at home. Spray painting aluminum is done in the following steps:
- Use a damp cloth and soap to wash the aluminum part. If there are any extra parts on it, remove them. Finally, dry the painted surface with a towel or napkins.
- Clean the surface with fine sandpaper. Cleaning with sandpaper will remove the oxide layer and smooth out uneven surfaces. If possible, sand the surface.
- Degrease the surface of the painted part. To do this, use white spirit, acetone or a similar degreasing liquid.
- Use a spray gun to apply the paint. If necessary, you can apply the paint by hand.
- Now you need to perform polymerization. You can use a high-temperature gas torch to melt the paint. The processing should be done in 2-3 stages to ensure complete polymerization of the coloring material.
