
Aluminum Composite Material (ACM) panels have become a popular choice for artists due to their durability, lightweight, and resistance to environmental damage. However, not all ACM panels are the same. The coatings applied to the surface play a significant role in how these panels perform for painting. This article explores the types of coatings available, their compatibility with various painting mediums, and how to make informed choices.
What Are Aluminum Composite Material (ACM) Panels?
ACM panels are constructed using two thin aluminum sheets bonded to a core. This core typically comprises either lightweight polyethylene (PE) or a mineral-filled material designed for fire resistance. Most artist-grade ACM panels feature a PE core due to its cost-effectiveness, stability, and ease of handling, making it ideal for artistic applications.
In contrast, mineral-filled cores, often referred to as fire-retardant (FR) cores, are made of polymer matrices like polyethylene or polypropylene infused with flame-retardant fillers such as aluminum trihydrate (ATH) or magnesium dihydrate (MDH). These FR cores provide enhanced fire resistance and are used in applications requiring strict safety standards, such as public buildings or commercial construction. While FR panels offer additional safety features, they are generally more expensive and less frequently marketed to artists, who typically favor PE cores for their lower cost and suitability for most artistic needs.
Aluminum composite material (ACM) panels consist of two thin sheets of aluminum bonded to a solid polyethylene core. The surface of the aluminum sheets is either coated with an organic coating or is anodized. The coating on each side can vary by manufacturer. Some artists' materials manufacturers sell ACM panels without a coating, only brushed metal or mill finish. Artists should prime or mount only on coated aluminum.
Specifications of Painting ACM Panels
ACM panels are typically available in standard thicknesses of 3mm, 4mm, and 6mm. The 4mm thickness is the industry standard for architectural applications, balancing durability and weight. The 6mm panels provide increased rigidity but are less commonly used due to higher costs and weight. The 3mm panels are generally reserved for signage and are the most common thickness for artistic use.
Standard panel dimensions often include widths of 50 inches (1270 mm) and 62 inches (1575 mm), with lengths of 122 inches (3099 mm), 146 inches (3708 mm), and 196 inches (4978 mm).
The aluminum sheets on ACM panels are commonly made from 3000 or 5000-series aluminum alloys, with a typical thickness of 0.020 inches (0.5 mm) per skin. These veneers are often coil-coated with high-performance finishes, such as fluoropolymer (PVDF or FEVE) coatings, or are anodized to ensure durability and aesthetic appeal.
When selecting ACM panels for artistic applications, the 3mm thickness with a PE core is generally preferred due to its balance of rigidity, lightweight properties, and cost-effectiveness. These panels can be displayed up to 30 inches (7623 mm) in both dimensions without support such as frames or cradling. However, 4mm thickness with a PE core or 6mm honeycomb core panels should be considered for larger projects. Standard dimensions and finishes vary by manufacturer, so it’s advisable to consult specific product specifications to ensure suitability for your intended use.
Honeycomb aluminum panels are an alternative to aluminum composite material (ACM) panels with solid cores.
Types of Coatings on ACM Panels
Anodized Aluminum Panels
Anodizing aluminum creates a protective oxide layer on the surface. This layer improves corrosion resistance and provides a smooth metallic finish. However, its smoothness can make it challenging for paints to adhere directly without preparation.
There are different types of anodized surfaces, including Type I (chromic acid), Type II (sulfuric acid), and Type III (hardcoat). These types vary in thickness, porosity, and durability, directly affecting their performance as a painting substrate. Unfortunately, artist materials suppliers do not specify the type of anodization used in their products, leaving artists uncertain about the surface’s characteristics. This lack of transparency makes it difficult to assess whether the panel is suitable for direct paint application or requires additional preparation.
Preparation of anodized aluminum for painting often involves lightly sanding or abrading the surface to create texture, followed by cleaning to remove residual debris or grease. While these steps enhance adhesion by providing a textured surface for primers and paints to adhere, they can also compromise the anodized aluminum’s protective oxide layer. The abrasion process may compromise the oxide coating’s integrity, potentially exposing the underlying aluminum to environmental factors like moisture and pollutants, which could accelerate corrosion over time.
Organic Coatings
Factory-applied coatings, such as polyester or coil-coated with high-performance finishes, such as fluoropolymer (PVDF or FEVE), are often used on commercial ACM panels. These coatings are durable and resistant to environmental factors, but they can create adhesion challenges for paint. Oil paints typically struggle to bond with these coatings unless treated with a primer. Acrylic paints adhere more easily but still benefit from additional preparation.
While these coatings provide a smooth surface, they may not meet archival standards unless specifically primed for the artist’s intended painting medium. For artists aiming for longevity, additional priming is necessary to create a stable foundation for paint.
The organic coating of ACM panels also requires preparation to receive a primer. However, this process will not compromise the integrity of the coating as long as the abrasion does not penetrate through the coating.
The brushed aluminum surface (also called “mill finish”) of the aluminum composite material (ACM) panel does not provide oxidation protection. It is highly susceptible to further oxidation, which may cause delamination and flaking of primer and paint.
Pre-Primed Panels with Artist-Grade Grounds
Pre-primed ACM panels for artists' applications are treated with grounds such as acrylic or oil primers tailored for specific painting mediums. These panels offer a ready-to-use surface, saving artists time and ensuring consistent results. For oil paints, pre-primed panels prevent common issues like sinking in or cracking. Acrylic gesso-primed panels provide excellent adhesion for acrylic paints.
However, most companies offering ACM panels for artists mount other substrates, such as canvas or paper, to the aluminum surface rather than offering pre-primed panels. Few companies, such as Artefex, provide pre-primed ACM panels that have undergone extensive testing to ensure their compatibility with various painting mediums. Artists seeking assurance in the longevity of their paintings will benefit from these tested and purpose-built options.
Testing and Transparency
One of the biggest challenges for artists is the lack of standardized testing and transparency from companies offering ACM panels for artists. Key tests include adhesion testing, accelerated aging, and environmental resistance evaluations.
Standard Adhesion Test
One standardized method for adhesion testing is the ASTM D3359 Standard Test Methods for Rating Adhesion by Tape Test. This test assesses the adhesion of a coating by scoring a grid pattern into the surface and applying adhesive tape to the area. The tape is then removed to determine how much of the coating detaches. The test is widely used because it provides precise and repeatable results, offering a reliable measure of a coating’s durability. Panels with published testing data, including results from standardized methods like this, give artists confidence in their longevity and performance.
For a complete explanation of adhesion testing for ACM panels and standard test methods, read The Importance of Adhesion Testing for ACM Panels as Painting Supports. |
Panels marketed as “ready-to-paint” without detailed specifications may perform inconsistently, especially under environmental stress. For instance, an artist reported that an unprimed panel exposed to fluctuating humidity and temperature began to delaminate within a year, with the paint layer peeling away due to insufficient adhesion. This example underscores the risks of relying on such panels without manufacturer testing data, emphasizing the need for verified transparency and preparation guidelines to ensure durability.
Claims such as “archival,” “premium quality,” or “acid free” are often not supported by published testing data. Suppliers rarely provide adhesion tests for common painting mediums or accelerated aging studies to verify long-term performance. This lack of evidence creates uncertainty about the reliability of these panels, especially under varying environmental conditions. Without verifiable data, artists are left to conduct their own tests or apply additional preparation, which can undermine the convenience these panels claim to offer.
The absence of detailed testing also makes it challenging for artists to trust claims of archival quality or durability. Manufacturers who invest in transparent testing processes and publish their findings enable artists to make informed, confident choices about the materials they use.
Priming ACM Panels for Painting
Priming is essential when preparing ACM panels with anodized or organic-coated surfaces for painting. Applying paint directly onto these unprimed panels often results in adhesion issues, which can compromise the artwork’s durability and longevity. Selecting the right primer tailored to ACM surfaces is critical to ensure optimal performance. However, many traditional primers are designed for canvas or wood and may not adhere effectively to aluminum substrates.
The Role of Priming in Enhancing Adhesion
Priming acts as a bridge between the smooth surface of ACM panels and the paint, creating a suitable substrate that secures the paint film. By using suitable primers tailored to the specific painting medium—such as alkyd-based grounds for oil paints or acrylic gesso for acrylics—artists can ensure both proper adhesion and long-term durability of their work. Different primers perform uniquely depending on the painting medium used. For oil paints, primers like alkyd-based grounds are particularly effective, as they provide the absorbent surface needed for proper adhesion while maintaining flexibility to prevent cracking over time. Acrylic paints, on the other hand, benefit from acrylic primers, which create a porous and flexible surface ideal for the water-based medium. Selecting the right primer tailored to the chosen medium ensures not only adhesion but also the long-term durability of the artwork.
Improper priming can lead to significant issues, particularly for oil and acrylic paints. Oil paints may peel or flake off over time when applied to an inadequately primed surface, as the non-porous aluminum does not provide the absorbency needed for proper adhesion. Similarly, while acrylic paints are more forgiving, they can still exhibit reduced durability and adhesion failure without a suitable primer. Proper priming ensures a stable, long-lasting foundation for both mediums, preventing delamination and preserving the integrity of the artwork.
Challenges in Selecting Suitable Primers
Finding a primer that adheres reliably to ACM panels is challenging due to the limited number of products specifically formulated and tested for such surfaces. Many commercially available primers are optimized for traditional substrates and lack testing on aluminum, leaving artists with little guidance when navigating this issue.
Tested Primers for ACM Panels
Despite the challenges, some manufacturers have tested and recommended primers for ACM surfaces. Notable examples include:
Rublev Colours Alkyd Grounds: Specifically formulated for ACM panels, this ground provides excellent adhesion and a smooth painting surface. It is particularly effective for oil paints, creating a durable and archival base. Rublev Colours has tested adhesion, demonstrating its compatibility with ACM substrates (Artefex; Natural Pigments).
Rublev Colours Tempera Ground: Also referred to as Rublev VAE Primer, this ground adheres well to ACM panels and supports various painting mediums, making it a reliable choice for artists seeking archival-quality preparation (Artefex; Natural Pigments).
Commercial Direct to Metal (DM) Primers: Golden Artist Colors recommends using commercial DM primers as a base coat on ACM panels. Proper surface preparation, including sanding and degreasing, ensures adhesion and durability (Just Paint).
The reliability of these primers has been demonstrated through tests specifically conducted for use on ACM panels. Such testing ensures that these products provide artists with dependable solutions for effectively and securely preparing ACM surfaces for painting.
Priming ACM panels is a crucial step to ensure proper adhesion and durability of the paint layer. Without an appropriate primer, artwork risks delamination and reduced longevity. To prepare their ACM panels effectively, artists should prioritize tested products like Rublev Colours Lead Alkyd Ground. When using other primers, conducting personal adhesion tests is advisable to confirm compatibility with the chosen painting medium.
Archival Considerations
For artists focused on creating long-lasting works, archival quality is essential. Several factors influence this:
Durability of the Aluminum Coating: Anodized surfaces resist corrosion but require preparation to receive priming for effective paint adhesion. The preparation of anodized coatings can damage its protective properties, rendering it susceptible to unstable oxidation and risking delamination of the primer and paint. Organic coatings, on the other hand, can be prepared to receive primers designed for artist paint without undue risk to the protective coating.
Chemical Stability: The interaction between paint and the coating impacts long-term stability. Pre-primed panels with artist-grade grounds provide the best results.
Environmental Resistance: Panels tested for humidity, UV exposure, and temperature changes ensure reliability for both indoor and outdoor artworks.
Making an Informed Choice
Artists choosing ACM panels should consider their medium, the panel’s surface preparation, and the transparency of the manufacturer. Panels with pre-applied, tested grounds are the best choice for professional and archival work. For panels marketed as “ready-to-paint,” additional preparation, such as sanding and priming, may be necessary to ensure durability.
Key testing data to look for includes adhesion ratings, which measure how well primers and paints bond to the surface under various conditions, and accelerated aging results, which simulate long-term exposure to environmental factors like humidity and UV light. By understanding these metrics, artists can ensure the longevity of their work and make informed decisions that align with their specific project requirements. These metrics provide valuable insight into the panel’s durability and suitability for archival-quality work, helping artists make informed decisions about their materials.
Bibliography
Artefex. “Art Panels and Archival Painting Supports.” Artefex. Last accessed January 20, 2025. Access online.
Summary: This source provides detailed insights into pre-primed ACM panels designed for artists, emphasizing archival quality and testing protocols.
Artefex. “How Well Do Grounds Adhere to ACM Panels?” Artefex. October 7, 2020. Last accessed January 20, 2025. Access online.
Summary: Report on standardized adhesion testing of Artefex pre-primed ACM panels.
Raymar. “Professional Art Panels.” Raymar. Last accessed January 20, 2025. Access online.
Summary: Discusses the use of premium materials in ACM panels and their suitability for art applications.
“Understanding Anodized Aluminum.” SAF. Last accessed January 20, 2025. Access online.
Summary: Explains the anodization process and its advantages and limitations for various applications.
Hunker. “How to Paint Over Anodized Aluminum.” Hunker. Last accessed January 20, 2025. Access online.
Summary: Details the challenges and preparation steps for painting on anodized aluminum.
Lorin Industries. “Anodized Aluminum vs. Painted Aluminum Coating Durability.” Lorin. Last accessed January 20, 2025. Access online.
Summary: Compares anodized and painted aluminum for durability and long-term performance.
Scott Bennett, Golden Artists Colors. "Painting on Dibond." Just Paint. February 2, 2016. Last accessed January 20, 2025. Access online.
Summary: Discusses the preparation of Dibond (a brand and trademark of ACM) for painting.
Greg Watson, Golden Artists Colors. "Painting with Oils on Non-Porous Substrates." Just Paint. December 10, 2020. Last accessed January 20, 2025. Access online.
Summary: Detailed discussion of preparing non-porous surfaces such as ACM for oil painting.
Stacy Brock, Golden Artists Colors. "Will It Stick? Simple Adhesion Testing In Your Studio." Just Paint. January 21, 2019. Last accessed January 20, 2025. Access online.
Summary: A simple adhesion test can be done in an artist's studio for little cost and time.
Artefex Primed and Canvas-Mounted ACM Panels
Frequently Asked Questions (FAQ) About ACM Painting Panels
What is an ACM panel, and why is it suitable for painting?
An ACM (Aluminum Composite Material) panel consists of two thin aluminum sheets bonded to a lightweight polyethylene or mineral-filled core. Its smooth surface, resistance to warping, and durability make it ideal for artistic applications, especially for large-scale or outdoor works.
Do I need to prime an ACM panel before painting?
Yes, priming is essential. Unprimed ACM panels can cause adhesion issues for both oil and acrylic paints. A suitable primer tailored to your painting medium creates a textured, absorbent layer that ensures proper adhesion and long-term durability.
What primers are best for ACM panels?
Some recommended primers include Rublev Colours Lead Alkyd Ground, Rublev Colours Tempera Ground, and commercial bonding primers like Golden Artist Colors Acrylic Gesso. These primers are tested for adhesion and durability on ACM panels.
Can I use oil paint directly on ACM panels?
No, applying oil paint directly onto ACM panels without priming can lead to peeling or flaking over time. A primer, such as an alkyd-based ground, provides the absorbent surface needed for proper adhesion and stability.
Are ACM panels archival for fine art?
ACM panels can be highly archival when prepared correctly with archival-grade primers and paints. Their resistance to warping, corrosion, and environmental changes makes them suitable for long-lasting artworks.
How do I prepare the surface of an ACM panel?
Begin by lightly sanding the panel to create texture, then clean it thoroughly to remove debris and grease. Apply a suitable primer for your medium to ensure proper adhesion and durability.
What are the limitations of painting on ACM panels?
While ACM panels are durable, they require proper priming and preparation. Additionally, some panels marketed as "ready-to-paint" may lack adequate testing for adhesion and long-term performance, necessitating additional preparation by the artist.
Can ACM panels be used for outdoor artwork?
Yes, ACM panels are highly suitable for outdoor artwork due to their resistance to environmental factors like moisture and UV radiation. However, use appropriate primers, paints, and protective coatings to maximize longevity.
As a result, some of the claims in the article are misleading. For instance, "Artists should prime or mount only on coated aluminum.". This is simply not true. The various forms of airbrush paint (e.g., Createx Wicked) that have been developed for the automotive community work perfectly well on bare (cleaned) aluminum panels. You can find many tutorials and videos of Craig Fraser and others painting directly on aluminum with the proper paints. A layer of primer or sealer is not going to hurt, but it is not always possible because in some cases you want the bare metal to be visible.
For instance, there is an entire art form devoted to brushed metal painting: the artist uses angle grinders and other tools to create patterns in the metal. Once the grinding is done, the artist cleans the substrate and paints on it with either water-based acrylic or solvent-based urethane (e.g., PPG, House of Kolor). Since the goal is to show the bare metal, they cannot use traditional primers. It is common to use a simple intercoat clear as a first layer for urethanes, and for water-based paints it is common to paint directly, to use a transparent sealer, or to apply a layer of water-based clear coat (e.g., Scenix clear) as a base layer. Traditional acrylic binders like Golden GAC200 will not work for this as they are not designed for adhesion to metal and they generally don't tolerate solvents (making it hard to put a 2K clear over top).
For traditional paints like Golden/Liquitex acrylics or oil paints, yes, I'd recommend a primer. However, I would not just slop on a traditional gesso or oil painting ground. I'd first apply a product that was designed for the particular type of metal substrate (steel, aluminum, copper). Of course you need to make sure that it is compatible with your paints and any further ground/gesso that you plan to put on top.
The simple truth is that paint chemistry has advanced significantly in the last half century. Automotive paints are now at the point where you can take your car out into the Arizona sun for years without issues. Oil paints or traditional acrylics wouldn't last even a small fraction of that time in extreme weather conditions. Modern solvent-based urethanes and water-based paints are simply superior, which is why they are used for industrial and automotive coatings. If you are painting on metal, you should pay attention to the communities that have been painting on metal for decades. Look into the specialist products that they have developed.
However, the context of the article is centered on artists employing traditional mediums such as oil, acrylic, watercolor, and egg tempera. These mediums differ significantly from industrual acrylic and ureathane paints in composition and behavior. Traditional paints generally lack the inherent adhesion properties required for direct application on non-porous surfaces like aluminum. Therefore, priming becomes essential to ensure proper adhesion and longevity of the artwork.
Regarding the practice of leaving portions of the metal exposed, it's important to consider the nature of aluminum's interaction with the environment. When exposed to air, aluminum forms a stable oxide layer that protects it from further corrosion. However, this oxide layer can be disrupted by environmental factors, leading to potential corrosion. Moreover, uncoated aluminum in contact with other materials can lead to galvanic corrosion, which may adversely affect adjacent painted areas.
In contrast, historical evidence shows that paintings on copper substrates have experienced failures, even when entirely covered by oil paint. This underscores the importance of appropriate surface preparation and the use of suitable primers to prevent long-term degradation.
While ACM panels have a proven track record in commercial and automotive art applications with direct-to-metal paints, artists using traditional mediums should adhere to the recommended practice of priming the panels. This approach ensures optimal adhesion and durability of the artwork, aligning with the material properties and historical precedents observed in fine art practices.
To further clarify, let us address a few specific points in your comment that may have led to misunderstandings about the article's intent:
1. "Artists should prime or mount only on coated aluminum"
This recommendation stems from the properties of traditional fine art paints, such as oil paints and acrylics intended for canvas and wood. These paints lack the advanced adhesion properties found in automotive and industrial coatings. Priming or coating aluminum ensures compatibility with these traditional paints and enhances the artwork’s longevity by providing a barrier against potential reactions between the metal and the paint over time.
While it is true that some modern paints—such as Createx Wicked or urethanes—can adhere directly to bare aluminum, these paints are outside the scope of traditional fine art practice. The statement in the article is aimed at fine artists, for whom using unprimed aluminum could result in poor adhesion or long-term stability issues.
2. "An entire art form devoted to brushed metal painting"
Techniques involving brushed metal, as described in your comment, are indeed fascinating and widely practiced in airbrush and automotive art. However, these methods prioritize the aesthetic use of the metal's surface as part of the final artwork. This approach often employs materials specifically designed to bond with metal, such as water-based clears or solvent-based urethanes.
In traditional art, however, substrates are typically seen as supports to be covered entirely by the artist’s medium, with priming serving to ensure adhesion and stability for that purpose. Of course, this does not prevent artists from adopting this aesthetic, but this may result in deterioation of the paint adjacent to exposed areas. This is area needs to be studied further, but we have seen issues of this nature on copper panels from the 15th through 17th centuries.
3. "Traditional acrylic binders like Golden GAC200 will not work for this"
We concur with your assessment that certain traditional fine art products are not suitable for direct application on metal, particularly if exposed to solvents. However, this reinforces the article’s central argument: traditional fine artists using ACM panels should rely on preparation methods and materials tailored for fine art purposes rather than assuming compatibility with techniques and materials developed for automotive or industrial applications.
4. "Modern solvent-based urethanes and water-based paints are superior"
The durability and advanced chemistry of modern industrial paints are undeniable. These materials are engineered for extreme durability in challenging environments, such as outdoor exposure and automotive applications. However, these characteristics are not synonymous with archival quality in fine art, where chemical stability and compatibility over centuries are of greater concern than resistance to extreme weather. Additionally, the visual and textural qualities of fine art paints, which are integral to their artistic appeal, often differ from those of industrial paints.
Your comment underscores the significant divergence between traditional fine art practices and commercial or industrial painting applications.
Thank you again for engaging with the article and sharing your insights. Your input helps foster a deeper understanding of the different ways artists work with ACM panels and how materials and techniques evolve across disciplines.