How to Custom Aluminum Extrusions Finishes?

Primary aluminum extrusion billets only have basic metal properties and are susceptible to oxidation, corrosion, discoloration, scratches and other problems when used exposed. Customized aluminum extrusion surface treatment is the core process to enhance the weather resistance, aesthetics, and service life of the profile, while adapting to different working conditions and design requirements.

This article will comprehensively dismantle the basic concept of aluminum extrusion surface treatment, processing necessity, mainstream surface technology, accurate selection methods, complete process flow, industry quality inspection standards, and post-care skills, to help buyers, engineers, manufacturers, one-stop solution for aluminum profile surface treatment customization, to avoid the selection and process misunderstandings.

What are Aluminum Extrusion Finishes?

Aluminum extrusion surface treatment refers to the post-treatment process of secondary deep-processing of the extruded billet surface that comes with the virgin aluminum billet after the aluminum profile has been extruded, cut, deburred and cleaned. Native aluminum profiles come with a very thin layer of natural oxide film from the factory, which has very poor protective ability and cannot meet the needs of outdoor, highly corrosive and abrasive scenarios.

All aluminum extrusion surface customization process, the core around the three main objectives:

Protective performance: isolate water vapor, salt, ultraviolet rays, chemical pollutants, and resist corrosion and abrasion.

Appearance beautification: customized colors, matte/mirror/brushed textures, wood grain textures, to match the design and brand vision.

Functional upgrading: improve stain resistance, insulation, high temperature resistance, suitable for special industrial use scenarios.

According to the processing principle, all the aluminum extrusions on the market can be divided into three major categories of surface treatment technology, clear distinction, selection at a glance:

Mechanical Surface Treatment

Without adding any coating materials, relying on physical grinding to change the surface texture of aluminum, only the surface physical modification. Commonly used processes include brushing, grinding, sandblasting, mirror polishing.

Process characteristics: to create a matte, brushed, mirror metal texture, can cover the profile surface of the small extrusion defects

Core advantages: no chemical pollution, strong environmental protection, retain the original metal texture

Applicable scenarios: interior decorative profiles, home aluminum accessories, products that need original metal appearance, often as a pretreatment process before anodic oxidation.

Chemical Surface Treatment

Relying on special chemical solution to etch and brighten the surface layer of aluminum, change the microscopic surface structure of aluminum, without covering thick coating. The mainstream process is chemical abrasion, chemical bright dipping.

Process characteristics: extremely high surface uniformity, matte frosted non-glare, high brightness mirror reflective effect is outstanding.

Core advantages: can handle complex shaped extruded section, subsequent with anodic oxidation adhesion greatly improved.

Applicable scenarios: high-end lamps and lanterns aluminum shell, architectural decoration pressure line, light luxury decorative aluminum profiles

Coating Surface Treatment

Covering the surface of aluminum extrusion with a layer of protective and decorative coating is currently the largest amount of industrial and architectural fields, the strongest protective performance of the custom process. It includes four mainstream processes: anodic oxidation, powder coating, electrophoretic coating and PVDF fluorocarbon coating. The protection ability is far beyond mechanical and chemical treatments, and is suitable for most of the harsh outdoor working conditions.

Why Finishing is Important for Aluminum Profiles

Many projects for the compression of costs, the direct use of billet aluminum extrusions, short-term seem to save money, the long-term will appear profile whitening oxidation, pitting, fading, wear and tear off the skin and other issues, significantly increasing the cost of after-sales replacement. Standardized custom surface treatment, is an indispensable part of the mass production of aluminum profiles landing, the core value is divided into four points:

Resist Erosion

Aluminum natural thin oxide film can not resist coastal salt spray, acid rain, ultraviolet rays, industrial dust corrosion. After professional surface treatment, a dense protective layer is formed on the surface of the profile, which can effectively eliminate the problems of surface pitting, oxidized whitening, and coating chalking, and is especially suitable for coastal buildings, outdoor photovoltaic racks, and open-air equipment racks.

Extend the Service Life of Aluminum Extrusions

The outdoor service life of billet aluminum extrusion without surface treatment is only 10-15 years; after high-quality anodic oxidation, powder coating and PVDF fluorocarbon treatment, the service life of the extrusion can be increased to 30-50 years, and there is almost no need for later maintenance. Long-term projects can significantly reduce the cost of replacement and artificial maintenance costs, while reducing the waste of aluminum, in line with the requirements of green building and environmental protection.

Take Into Account the Practical Function and Appearance Customization Needs

Functionality: Enhance the surface hardness, scratch resistance, waterproof sealing, and part of the special process can realize anti-static, insulation, antibacterial function;

Appearance level: tens of thousands of customized colors, wood grain, frosted, high-gloss, matte texture, perfectly matching the design of the building facade, corporate brand color matching, home appliance appearance aesthetic needs.

Meet the Industry’s Mandatory Acceptance Standards

Products such as architectural doors and windows, curtain walls, new energy aluminum profiles, etc. must pass international authoritative testing and certification such as AAMA, Qualicoat, ISO, ASTM, and so on. Compliant surface treatment process is a mandatory prerequisite for the project to pass LEED, BREEAM green building certification, doors, windows and curtain walls industry acceptance, as well as a necessary condition for the product warranty to take effect.

Main Types of Custom Aluminum Extrusion Finishes

Combined with the market shipments, cost-effective, protection level, the following list of 8 commonly used aluminum extrusion custom surface process, compare the advantages and disadvantages and applicable scenarios, to facilitate direct selection.

Raw Surface

Aluminum extrusion is cut directly without any subsequent processing, presenting a natural silver-gray metal surface.

Advantage: lowest cost, 100% recyclable, no coating pollution.

Disadvantages: easy to leave fingerprints, easy to oxidize white, no color options, weak corrosion resistance.

Applicable scenarios: hidden racks inside the equipment, industrial support structures, semi-finished profiles that need secondary processing later on.

Anodic Oxidation Treatment

Adopting electrochemical process, thickening the native oxide film of aluminum, the coating is integrated with the aluminum substrate and will not peel off. It is divided into three major subdivided types: native anode, color anode and hard anode.

Native color anode: retaining the original color of metal, transparent protective film, restoring the original texture of aluminum.

Color anode: black, bronze, gold and other conventional colors, the color penetrates into the oxidation film, never lose color.

Hard anode: film thickness up to 25-50μm, high surface hardness, extreme anti-wear.

Core advantages: environmentally friendly, no VOC, adhesion, excellent weather resistance, high metal texture;

Applicable scenes: architectural doors and windows, electronic shells, industrial wear-resistant fittings, high-end decorative profiles.

Powder Coating

Electrostatic spraying solid powder coating, high-temperature curing molding, is currently the most cost-effective surface customization process for architectural aluminum profiles. It supports all RAL color card color matching, and matte, glossy and orange peel texture can be customized.

Core advantages: unlimited color choices, scratch-resistant and wear-resistant, high production efficiency, less waste and more environmentally friendly;

Shortcomings: metal translucent texture is weaker than anodic oxidation;

Applicable scenes: civil doors and windows, indoor partitions, common building facades

Electrophoretic Coating

Aluminum profiles are immersed in water-based electrophoresis paint liquid, and the electricity is turned on to make the paint film uniformly adhered to the profile surface, and the coating can be achieved without dead angle even for complex shaped sections. The surface is smooth and bright, and the paint film is fine and even.

Applicable scenes: high-end doors and windows, automobile decorative aluminum bars, lighting shell, light luxury home decoration aluminum profiles

PVDF Fluorocarbon Spraying

The industry’s top outdoor protective coating is divided into primer + topcoat double-layer spraying, high temperature resistance, UV resistance, acid and alkali corrosion resistance, outdoor warranty of up to 30-50 years.

Applicable scenes: ultra-high-rise curtain wall, coastal high salt spray area building, extreme climate outdoor aluminum profiles, large landmark building facade

Drawing Treatment

Mechanical unidirectional drawing forms uniform hairline texture, which can hide daily light scratches and fingerprints, minimalist industrial style appearance. Often used with anodizing to enhance protection.

Mirror Polished

Multi-channel fine polishing + buff treatment, to realize the mirror reflection effect, the value of the full, no coating coverage, pure metal mirror texture, mostly used for high-end decorative parts.

Wood Grain Transfer

On the powder coating substrate, through the thermal transfer process to reproduce the simulation of wood grain texture, both the ruggedness and durability of aluminum and the natural appearance of wood, to eliminate the problem of mold, deformation, insect moths, free of daily maintenance.

Scenarios: wood-like doors and windows, indoor curtain wall, courtyard aluminum fence, high-end furniture aluminum frame.

Powder coating vs. Anodic Oxidation Treatment

Powder coating and anodic oxidation are the two surface processes with the highest usage rate in the customization of aluminum extrusion, and the two are applicable to the scene and performance differences are obvious, the following is a visual comparison from four core dimensions to facilitate quick selection:

Visual Effect of Appearance

Powder coating color matching covers all categories of RAL color card, matte, glossy, orange peel, frosted and other special textures can be customized, high color fullness, but completely cover the metal texture of aluminum itself, there is no translucent metal texture;

Anodic oxidation relying on the original surface layer of aluminum into a film, complete retention of high-level translucent metal color, the overall texture is more simple and advanced, can only achieve the basic monochrome, bronze, black, gold and other conventional color matching, color richness is far less than powder coating.

Outdoor Weathering Performance

Standard powder coating can meet the common outdoor sun and rain scenarios, long-term outdoor use after 3-5 years is prone to slight loss of light, chalking phenomenon; anodic oxidation film layer and the aluminum substrate into one, anti-ultraviolet rays, resistance to rain erosion is stronger, long-term outdoor use is not easy to fade, not easy to chalking, weathering stability is more outstanding.

Surface Hardness and Scratch Resistance

Conventional powder coating has medium hardness, so it is easy to produce scratches and coating damage in daily knocking; anodized oxide film has higher hardness, especially hard anodized process, with leading anti-friction and anti-scratch performance, which is more suitable for crowded and easy to produce friction and knocking use scenarios.

Customized Production Cost

Large quantities of conventional solid color powder coating process is mature, high production efficiency, lower cost per piece, cost-effective advantage; anodic oxidation of the basic model pricing is moderate, but customized dark colors, thick film hard oxidation, special color matching, the complexity of the production process to enhance the overall cost will be significantly higher than the powder coating.

How to Choose the Right Aluminum Extrusion Finish

Customized surface treatment need not blindly pursue the highest specifications, combined with the use of the environment, functional needs, appearance requirements, budget four dimensions of the selection, the best cost-effective.

Selection According to the Use of the Environment

The use of the environment is the core factor in determining the level of surface treatment, different humidity, corrosive media, light intensity, the tolerance requirements of the protective layer of the profile are very different.

Indoor dry and dust-free environment, no rain, salt spray, ultraviolet erosion, the choice of blank surface, color anodic oxidation or ordinary powder coating can be, while controlling the cost to meet the basic aesthetic needs;

Conventional outdoor open-air scenes, long-term rain wash and sunlight exposure, priority color anodic oxidation or standard powder coating, can withstand daily climate aging, to meet the requirements of outdoor use of civil building foundations;

Coastal salt spray areas, chemical parks and other strong corrosive environments, salt and acidic and alkaline substances will quickly penetrate the ordinary coating, must choose PVDF fluorocarbon spraying or thickened sealing type anodic oxidation, resolutely avoiding ordinary powder spraying, to avoid short-term bulging of coatings and corrosion of the substrate;

Plateau, unobstructed facade and other strong ultraviolet direct light scenes, long-term exposure to the sun is very easy to make the ordinary coating loss of light and fade, give priority to the top of the weathering PVDF fluorocarbon spraying, to protect the long-term appearance of the profile is stable.

Selection According to Functional Performance

In addition to protection and aesthetics, some aluminum extrusions have special physical property requirements, which need to be matched with targeted processes: frequent friction, opening and closing collision of highly wear-resistant fittings, such as equipment slides, door and window handles, the choice of hard anodized, relying on the high hardness of the oxidized film to withstand the continuous wear and tear;

For electrical enclosures and electronic control chassis that require insulation protection, thick film anodizing comes with stable insulating properties, and special insulating powder coating can also meet electrical safety standards;

Aluminum profiles that have been in the vicinity of high-temperature equipments for a long time are prone to aging and cracking of organic spray coatings, while the anodic oxidation inorganic film layer has a better performance of high-temperature resistance, which is suitable for long-term use in high-temperature working conditions.

Selection According to Appearance Design

Appearance style directly determines the direction of the process, accurate matching of the design scheme can be: if you need thousands of custom colors, special matte / orange peel texture products, powder coating is the only choice, the color coverage is not limited;

Preferring minimalist modern style, if you want to retain the translucent texture of the original aluminum metal, give priority to the original color/brushed anodic oxidation, the texture is high-level and durable;

If you want to reproduce the texture of solid wood and replace the easily deformed and decayed solid wood profiles, you can directly choose the wood grain heat transfer process; if you want to pursue the visual effect of high brightness mirror surface for high-end decorative accessories and display profiles, you can use the mirror surface polishing process.

Selection According to Budget and Mass Production Scale

In terms of cost gradient, the overall cost of each type of process, from low to high, is as follows: rough surface ＜native anode ＜color anode ＜standard powder coating ＜wood grain transfer ＜hard anode ＜PVDF fluorocarbon spraying.

In terms of production efficiency, powder coating has a high degree of automation, a short production cycle for mass production orders, and a lower cost per piece, which is suitable for doors, windows, curtain walls and other bulk projects;

Anodic oxidation, electrophoresis coating customization flexibility is stronger, small quantities of high-end custom orders more suitable, but special color matching, thick film oxidation will synchronize with the higher production costs.

Aluminum Extrusion Finishing Process

All high-end surface treatment process, are inseparable from the pre-treatment, coating processing, curing, quality inspection of the four core steps, pre-treatment directly determines the coating adhesion, 80% of the surface quality defects are from the pre-treatment is not in place.

Surface Pretreatment

Degreasing cleaning: through the acid and alkali cleaning pool, to remove extrusion residual lubricants, surface dust and oil, to avoid the coating off, pinhole defects

Chemical etching: Remove the original weak oxidation layer of aluminum, create a microscopic rough surface, and improve the coating fit.

Dust Removal and Neutralization: Remove etching residual black hanging dust, to ensure the subsequent coating color uniformity and no color difference.

Customized Surface Coating Process

Anodic oxidation process: into the electrolytic cell energized oxidation → microporous adsorption of dyes → high temperature sealing closed microporous, the coating and the aluminum material one-piece molding

Powder coating process: electrostatic spray gun adsorption of powder → profile surface uniform powder coating → high temperature oven curing film

Electrophoresis/Fluorocarbon spraying process: immersion painting/multi-layer spraying primer top coat → uniform coverage of complex cross-section profiles

High-Temperature Curing and Molding

Precise high-temperature curing is indispensable for coating adhesion molding, and different surface processes are matched with exclusive baking temperatures: the standard curing temperature of powder coating is 180-200℃, the curing temperature of electrophoretic coating is slightly lower, and PVDF fluorocarbon coating requires segmented high-temperature baking to guarantee the denseness of the coating.

High-temperature fusible coating raw materials, so that the paint film and aluminum substrate firmly combined to completely eliminate the coating hollow drum, adhesion and lack of hidden trouble, and comprehensively improve the profile resistance to bumping, flaking and weather resistance.

Full-Dimensional Factory Quality Inspection

After all the processing procedures are completed, the finished aluminum extrusions need to carry out standardized tests one by one to control the quality in all aspects from appearance, performance and durability: the film thickness test checks whether the coating thickness is up to the standard to avoid cutting corners; the 100-gauge adhesion test verifies the adhesive strength of the coating;

Salt spray test simulates coastal corrosive conditions to check the anti-corrosion ability; color difference and friction test control the consistency of the appearance and daily scratch-resistant performance, respectively, all the indexes are qualified before shipping into the warehouse to ensure that the finished product fully meets the international industry acceptance standards.

Quality Standards for Aluminum Finishes

Purchasing and acceptance can be directly compared with the following three major international common standards, to avoid suppliers cutting corners and film thickness does not meet the standard:

ISO International Standard

As a global benchmark for the aluminum industry, it is suitable for the trade and project acceptance of all aluminum extrusions at home and abroad, with no geographical restriction. Among them, ISO 7599 specifically controls anodized profiles, specifying three hard indicators: oxide film thickness, sealing quality and appearance defects, which are mandatory inspection standards for anodized products;

ISO 2106 standardizes the testing method of oxide film thickness to ensure the accuracy of testing data;

ISO 18768 for powder coating of aluminum profiles, constraining the adhesion, impact resistance and chemical resistance of the coating, no matter for domestic projects or cross-border export orders, the goods can be inspected in accordance with this set of standards.

Qualicoat Coating Certification

The most recognized special certification in the field of global architectural aluminum spraying, focusing on organic powder coating, fluorocarbon spraying quality control, according to the corrosion intensity of the working conditions are divided into three levels: Class1 is suitable for indoor dry and non-corrosive scenarios;

Class2 is suitable for common outdoor open-air environment, meeting the use of conventional doors, windows and facades;

Class3 is a special grade for seashore, targeting high corrosion scenarios such as coastal salt spray, chemical exhaust gas, etc., which requires a significant increase in the denseness of the coating and the length of time for salt spray resistance.

High-end curtain wall and coastal construction projects usually force suppliers to provide valid certification reports.

AAMA North American Architectural Aluminum Standard

Widely used in the North American market and domestic and foreign sales of architectural aluminum profile projects, focusing on outdoor real weathering performance, three grades are clearly delineated, and can be directly selected according to the project site selection:

AAMA 2603 is an entry-level basic coating, suitable only for indoor scenes without wind and rain erosion;

AAMA 2604 belongs to the middle and high end outdoor standard, which can guarantee 5 years of outdoor use without obvious loss of light and chalking, and is suitable for general civil outdoor projects;

AAMA 2605 is the top standard of architectural aluminum spraying, with 10-year official color and light warranty, anti-ultraviolet ray and anti-aging performance, it is the first choice of acceptance standard for super-high-rise landmark curtain wall and long-term unobstructed facade.

Common Industries Using Finished Aluminum Extrusions

Architectural Industry

Door and window frames, glass curtain walls, sunshade louvers, balcony guardrail, accounting for more than 60% of the market share of aluminum extrusions, mainly powder coating, anodic oxidation, PVDF fluorocarbon, wood grain transfer process.

Automobile Manufacturing Industry

Roof racks, chassis extrusion profiles, aluminum shells for new energy batteries, interior decorative compression strips, mostly with hard anodic and electrophoretic coating, taking into account the needs of lightweight and corrosion resistance.

New Energy Photovoltaic Industry

Photovoltaic frame, photovoltaic tracking bracket, perennial outdoor exposure to the sun, standard PVDF fluorocarbon, high weathering powder coating, long-term resistance to ultraviolet rays without fading.

Electronic Home Appliance Industry

Notebook shells, heat sinks, LED light shells, mainly brushed anodized, mirror polished, taking into account the heat dissipation performance and appearance value.

Industrial Automation Industry

Equipment racks, assembly line frames, protective fences, the conventional choice of natural color anodizing, cost-effective, easy to clean, wear-resistant and durable.

Maintenance Tips for Finished Aluminum Extrusions

High-quality surface treatment with proper maintenance can further extend the service life of the profile and reduce maintenance costs:

Daily Cleaning Specification

Regular environment: clean every 3-6 months;

Coastal and industrial areas: rinse with water every 1-2 months for salt and dust.

Cleaning method: warm water with neutral detergent, use a soft cloth to wipe, prohibit steel wire balls, abrasive sponges and hard objects to scrape.

Taboo: Strong acid and alkali cleaning agents, high-pressure water gun close to the coating, to avoid damage to the sealing layer and paint film.

Anti-Corrosion Protection Points

Coastal areas regularly fresh water rinse salt spray residue, to prevent salt penetration corrosion.

Avoid direct contact between aluminum and steel and other dissimilar metals to prevent galvanic corrosion.

Protective film is attached during construction to avoid scratching the surface coating.

Exclusive Maintenance of Sub-Processes

Anodized profiles: no special maintenance, daily wipe with water, almost zero maintenance.

Powder coating/wood grain transfer: small scratches can be repaired with the original paint refinishing pen.

PVDF fluorocarbon profile: ultra-low maintenance requirements, no need for frequent maintenance in extreme climates.

Hardware Maintenance

Doors, windows, movable aluminum profile hinges and pulleys are filled with silicone-based lubricant once a year, and the sealing tape is replaced once in 5-10 years to ensure the overall use of sealing.

Conclusion

Aluminum extrusion surface treatment customization is not a universal program, only the most suitable program: indoor decoration value value optional brushed, electrophoresis; general outdoor projects preferred cost-effective powder coating; coastal and landmark curtain wall approved PVDF fluorocarbon spraying; the pursuit of metal native texture priority anodic oxidation.

When customizing the surface treatment of aluminum extrusions, be sure to combine the four dimensions of the use of the environment, functional needs, appearance and color, project budget selection, while checking the film thickness, industry certification standards, from the source to avoid the surface peeling, discoloration, corrosion and other quality problems, taking into account the aesthetics of the product, service life and the overall cost of the project.