When you’re working with aluminum components, it’s vital to consider whether the pieces need engineered coatings to give the performance specifics you need and want. Those specialized layers could bring desirable results by protecting the surface underneath, plus providing additional characteristics that promote or prevent certain scenarios.
Here are five examples of engineered coatings that work well for aluminum or aluminum alloys.
They’ll give you some valuable inspiration for thinking about possibilities associated with your aluminum parts and highlight how necessary it is to think about how the aluminum components you want to coat will get used.
1. Polyvinylidene Fluoride (PVDF) Resin
Polyvinylidene fluoride (PVDF) resin is an engineered coating often used for architectural applications due to its excellent weather resistance. Aluminum roof sheets and wall claddings are some of the most common components that get coated with PVDF.
It’s also possible to get PVDF coatings infused with pigments, such as to match other parts of a building’s exterior or complement the look of the surrounding structures. Since PVDF coatings also resist fading, corrosion, and chalking, they’re good choices for aluminum components in highly noticeable areas, such as on building exteriors.
One example involved the Federal Building in Hawthorne, California. The structure, completed in 1972, features anodized aluminum panels and glass wrapped around concrete. Those design characteristics give the building a mirror-like finish. But, since time is typically unkind to many outdoor surfaces that encounter the weather, a team had to take action to preserve the building’s appearance.
An examination of the building before a recent improvement project showed that people had coated the aluminum with silver paint several times over the years. However, it flaked off, and the effect was so severe in some cases that it exposed the aluminum to the elements.
The team overseeing the building’s renovations applied an engineered water-based PVDF coating to the aluminum. The additive was a custom color to match the aluminum’s original hue. The work also included using a silicone sealant to give the coating a lifespan of at least two to three decades.
2. Henna Extract-Infused Paint
The best coatings for aluminum are not always the ones people most expect. In one example, a researcher tested the effectiveness of coating aluminum alloys with henna leaf extract mixed into a paint.
The investigation involved testing aluminum alloy 5083 in a simulated environment that exposed the pieces to saltwater. Aluminum is a popular choice in the maritime industry. However, there are ongoing efforts to protect the material from corrosion due to the near-constant saltwater exposure.
The researchers created three henna leaf-infused paints to determine the optimal mixture. The results showed that making a coating with 10% henna leaf extract showed the best performance for curbing corrosion.
Other options exist for managing corrosion, too. Titanium alloys resist corrosion, making them popular choices for marine use. Aluminum-titanium alloys are often chosen when the goal is to make lightweight components. Since many industries need corrosion-resistant aluminum, making a coating or alloy to meet specific requirements is often the best bet.
3. Specialty Anodic Coatings
People commonly apply anodic coatings to aluminum medical devices to improve their lifespan and reduce the abrasive effect that prolonged and regular use can cause.
However, stipulations for medical-grade anodic coatings state that they must tolerate 50-100 cycles of sterilization with vaporized hydrogen peroxide or peracetic acid or the use of a high-alkaline cleaner without showing color degradation or a breakdown of the coating.
Thus, many companies catering to the medical device industry offer specialized anodic coatings that withstand such sterilization regimens and provide other desirable characteristics. For example, some are biocompatible.
One company has an engineered polytetrafluoroethylene (PTFE) coating suitable for permanently marking the aluminum device during the application. That characteristic makes a coated product easy to trace or establish ownership of when needed.
4. Low Interfacial Toughness (LIT) Coatings
Aluminum is the Earth’s third most abundant element. It’s also widely used in a wide variety of products. Perhaps that’s why researchers commonly experiment with aluminum when aiming to come up with new engineered coatings. They know that if the layer of material works as expected on aluminum, that’s already an indicator of excellent progress.
Researchers at the University of Michigan sought to develop a coating for aluminum and other surfaces that would cause a de-icing effect. They ended up with a spray-on material that offered low interfacial toughness (LIT). LIT encourages cracks to form between the icy surface and the ice itself. Then, instead of ice adhering to whatever’s underneath, it slides off, similar to food cooked in a non-stick pan.
The team developed an assortment of possible LIT coatings to use. They then tested them on various surfaces, including a large aluminum sheet and a piece of thin aluminum mimicking a power line. Tests showed that the ice fell off immediately due to its weight.
Conversely, the ice stayed stuck to the control group surfaces. That was even the case with material coated with an ice-phobic substance. The researchers need to do more research to enhance the performance and see what happens with other surfaces. In any case, this example shows the promise of engineered coatings when scientists have a clear goal in mind.
5. Germicidal and Antimicrobial Coatings
Aluminum components may also need germ-killing coatings or those that curb bacterial growth. For example, some aluminum parts of climate control equipment feature antimicrobial coatings to prevent mold formation.
It’s also increasingly common for aluminum food packaging to include coatings that stop bacteria from flourishing. Aluminum does not offer such properties on its own, but when specialty coatings are easy to apply, they become appealing for a wide variety of reasons.
A Texas A&M University team created a hydrophobic antimicrobial surface coating that can reportedly help the underlying surfaces retain their germicidal properties for longer. The researchers were particularly interested in using their invention to safeguard against the cross-contamination of surfaces regularly used to handle food.
Many of them, such as produce buckets and conveyor belts, often contain aluminum. That’s why the researchers used aluminum as their testing material for an engineered coating made from silica and a naturally occurring germicidal protein called lysozyme.
They started by placing a layer of silica on the aluminum using high heat, then adding a silica-lysozyme coating to that surface. The silica-aluminum substrate bound with the new layer, creating a coating with microscopic roughness that gave the hydrophobic quality. When testing it against salmonella and listeria, the coated surfaces had a 99.99% lower prevalence of the bacteria than the non-coated ones.
Careful Consideration Brings Favorable Results
There’s no single best engineered coating for all aluminum components or alloys. However, people are likely to get the best results when they think about their goals. For example, must the treated aluminum offer corrosion resistance, or are you trying to prevent bacteria buildup? Having a clear idea of what you want to accomplish with an engineered coating will steer your efforts while creating a new one or choosing an existing option for your metal surface.