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Aluminum is a metal that at low loads does not require painting and is considered a non-ferrous metal. The reason it does not require painting is that it will automatically surround itself with an aluminum oxide layer that protects the metal from any weather-linked influences. In the following article, we will go into detail why sometimes it can prove beneficial to paint aluminum and when doing so which is the best paint to use.
Table of Contents
- 1 Applications for Aluminum Paint
- 2 Difference Between Anodized and Non-Anodized Aluminum
- 3 Materials Required for Painting Aluminum
- 4 What to Look for When Buying Primer and Paint for Aluminum
- 5 How to Paint Aluminum
- 6 Tips and Tricks for Painting Aluminum
- 7 Aluminum Paint Safety Instructions
- 8 Frequently Asked Questions
Applications for Aluminum Paint
What is great about aluminum is that unlike other metals it does not have to have any additional protection from external influences as it forms its layer of protection being a layer of aluminum oxide. As long as the layer is abraded it renews itself often. Just note that this aluminum oxide layer is not of high optical quality as it is grey and isn’t particularly aesthetically pleasing. So, in certain cases, one may want to paint the aluminum to make it look prettier. Aluminum paint can also be used when the non-ferrous aluminum is exposed to any chemicals with a high pH value (high is considered 8.5 or higher).
Finally, if your aluminum is regularly in contact with steel, copper, brass, or bronze while under the influence of moisture then we strongly recommend you protect it with paint.
Difference Between Anodized and Non-Anodized Aluminum
When you surface pre-treat aluminum, it is then referred to as anodized (previously was called anodic oxidizing). The pre-treatment is when an oxide layer through an electrochemical process, is applied to the material. The aluminum itself causes this oxide layer to form and it isn’t something that you have to apply.
The layer is fused to the aluminum and its protective layer offers protection from both the inside and the outside of the aluminum. Depending on the desired use for the aluminum the layer thickness varies, the higher the stress on the component determines the thickness of the anodized layer a thickness anywhere between five and twenty-five micrometers. Once your aluminum has been anodized it makes the metal very resistant to corrosion and weathering. Anodized aluminum has greater longevity and the material as a whole is preserved longer.
It is imperative to prepare your surface sufficiently before you attempt painting anodized aluminum this is necessary as to paint anodized aluminum the oxide layer has to be scrubbed off completely (you may need to sandblast it to achieve this). We will go into more detail on how to paint anodized aluminum later in this article. If you are simply looking to change the color appearance of your aluminum you can simply anodize it a second time as you can select different colors.
Materials Required for Painting Aluminum
If you choose to paint your aluminum you will require the following materials:
- You can use either a spray gun, foam roller, or brush
- Sanding fleece or sandpaper
- A degreaser (such as acetone or methylated spirits)
What to Look for When Buying Primer and Paint for Aluminum
You need to take into consideration the load your material will be subjected to determine which paint you select for your aluminum. If you are simply looking to alter the appearance and your load will be relatively low then you can select a paint with just one component ideal for lower stress. Powered coating or two-component coatings are suggested for aluminum when the metal will be exposed to mechanical influences or high weather-related influences such as aluminum utilized in boat building.
Understandably two-component coatings are pricier than the one-component coating options but spending the extra money is worth it as the two-component coating has a greater resistance to external influences and solvents. One negative aspect of two-component coatings is that you need to apply it very quickly and you have to ensure to mix it with the perfect ratio, overall, you have a very limited processing time.
Always ensure your aluminum paint and primer are compatible we suggest you use products from the same brand.
How to Paint Aluminum
You will have to handle your aluminum the same way for painting it as bonding and ensure the protective oxide layer is completely removed first before you can begin applying any paint. This can be a difficult task especially if the surface area is vast as the oxide layer will continue to renew itself.
Aluminum Grinding as Surface Preparation
You can use several different options to remove the oxide layer such as sandblasting it or grinding the aluminum. Sandblasting can be very expensive especially if you have to tackle a large area. Another option is to remove the oxide layer using chemicals but this can be toxic for one’s health, your best option is to simply use sandpaper to sand down the surface.
You can once you have sanded the aluminum choose to polish the surface giving it a high-gloss finish, or you can simply leave it rough. If you are going to polish it first you can use coarse grit sandpaper and then slowly change to a finer option but keep in mind if you choose to go this route, we do not recommend painting the aluminum bit rather finishing it with a polishing paste and then an aluminum clear coating.
If you will be painting the aluminum you can remove the oxide layer using sandpaper that has a coarse grit. Ensure you remove all dirt and dust before you begin sanding, otherwise, the sanding will cause any remaining dirt and dust to be embedded in the aluminum. When you have completely sanded down the aluminum you will need to once again clean off any dust before you can begin painting.
We recommend you use spirits to degrease the surface you can use a lint-free cloth to apply it and rub-down the whole surface. Ensure you wear protective gloves as your finger grease can negatively affect how the paint adheres to the surface.
Apply Aluminum Primer
You will have to apply an aluminum primer before you can start applying the aluminum paint, it can be very difficult to paint aluminum as the paint struggles to adhere to the surface sufficiently. A primer is also known as an adhesion promotor which allows the aluminum paint to adhere sufficiently to the surface. You can use a brush, spray gun, or roller to apply your aluminum primer to the surface.
Application of Aluminum Paint
Always ensure that your primer has completely dried before you start painting the surface. Always consult the manufacturer’s datasheet before beginning to paint as it will advise the best method to paint that particular brand. The finish is already included in a two-component paint but if you use any other form of paint, we suggest several coats be applied to ensure that you have completely sealed the surface. Ensure that your products are compatible when selecting your finish.
Use a roller and in a crosswise direction apply the aluminum coating this will ensure that the paint is applied quickly in first a longitudinal direction followed by a transverse direction and finally once again in a longitudinal direction. Do this process without picking up new paint and once completed immediately use a brush to smooth out the paint. Hold your brush at a gentle angle and smooth out the surface brush marks that may show but do not worry about this as once the paint dries, it will vanish.
Multi-Layer Coating Application
If you have chosen to use a product that is not a two-in-one product then it will be necessary to apply several coats, if so, you should follow the following process: Ensure your primer coat is completely dry this can take roughly 24 hours, then gently sand down the varnish lightly using fine-grit sandpaper. Next, you can apply an additional coat of varnish to continue like this until you have applied all the necessary layers. Finally, you can apply aluminum paint which will further protect the material.
Painting Anodized Aluminum
It is much easier to paint non-anodized aluminum as anodized aluminum has its protective layer on which needs to be completely removed before you can attempt to paint the metal. You will have to completely sand off the adonized layer otherwise you run the risk of your paint chipping.
The best option to remove is to use either the glass bead blasting process or mechanically sandblasting, the glass bead option should only be performed by a specialized professional. Aluminum must be smooth before you begin any application. If you choose to sandblast the metal it will leave a rough surface so you will have to polish the surface smoothly once you have finished sandblasting. Glass bead blasting will leave the surface smooth so no polishing will be necessary.
You can choose to remove the anodized layer using chemical removal more specifically, nitric acid but due to the potential health risks we strongly recommend as a private user you do not attempt this.
A great tip is to use a pipe cleaner that is commercially available to remove the anodized layer, it contains roughly 20% sodium hydroxide. Place the pipe cleaner in a stable container ensuring the bottom is covered to a height of roughly 3 millimeters and then pour two-thirds full of the container with warm water. Stir so that the powder dissolves and then take the aluminum component and immerse it in the mixture. Swirl the piece around until such a time that the water-pipe cleaner liquid color has changed. This mixture is highly corrosive so ensure to use plastic tongs and never your bare hands.
It will only take a couple of seconds for the anodized layer to be completely removed then you can rinse the piece under warm running water. If there is any residual anodized layer remaining you will then be able to rub it off using an ordinary household sponge. The mixture as advised is very corrosive so occupational safety is paramount to ensure you do the work outside and wear the necessary safety gear such as protective goggles, gloves, and a respirator. You must never touch the mixture with your bare hands!
Tips and Tricks for Painting Aluminum
You have to make sure the area you are working in, and the surface of the aluminum are completely clean before you begin painting aluminum. If there is any dust it will be incorporated into the paint and will ruin your finish. You can use a lint-free cloth to wipe down the surface before you start varnishing it.
Just like when you are varnishing wood, when you varnish aluminum do not use a hairy brush as every single hair will be visible, rather use specifically developed brushes of higher quality.
Also do not use cloths or sandpaper which has already been used on other metals as this could cause very fine particles to become incorporated into the aluminum which will negatively affect the appearance.
If you choose to use spray paint which can be a great option to cover hard-to-reach places ensure you do the same pretreating as you would for paint.
Aluminum Paint Safety Instructions
There is always some danger when working with varnishes, paints, and adhesives so you need to consider your safety, ensure you are wearing the following safety equipment:
- Disposable gloves ideally made of nitrile
- Clothing that is long-sleeved clothing
- Safety goggles
- A respirator mask
Rather work outside but if you cannot then ensure your work area has good ventilation particularly as sometimes the painted objects will only lose their bad odor when it has evaporated.
Do not allow any varnish to come into contact with your eyes or mucous membranes if for any reason this does occur you need to wash the affected area immediately and then consult a doctor. Provide your doctor with the product’s datasheet so that they are aware of all the ingredients and can prescribe the appropriate treatment.
Frequently Asked Questions
How Does one Protect Aluminum?
You can protect aluminum in several ways such as anodizing the aluminum or priming it or painting or powder coating it. Which method you choose to use is dictated by your required use of the aluminum component.
What is the Best Paint for Aluminum?
To select the best paint for aluminum you first need to determine what your use for the aluminum component will be. Heavy stresses will require a two-component paint, while you only need to use a one-component paint on a weaker stressor.
Are you Allowed to Powder Coat Aluminum?
You can powder coat aluminum this is an alternative option to painting aluminum or anodizing it. Powder coating aluminum provides a top-quality protective layer against mechanical and weather-related influences and chemicals.
Which is the Best Aluminum Primer?
You will require a specialized aluminum primer to prime aluminum as once the aluminum has been sanded a universal primer will not adhere to the surface.
How Does one Paint Aluminum Allow Wheel Rims?
You use the same procedure you would paint any other aluminum, and as always surface preparation is imperative and ensuring that each layer of paint is completely dry before beginning to apply the next layer. If you have damage to your rims that is deeper than 2 millimeters unfortunately there is no salvaging it as it is a potential safety risk when driving, sadly the rims will need to be disposed of.
It is not too difficult to paint aluminum as long as you follow the guide accordingly!