Architectural aluminum finishing
1 Who is it useful to know and why?
Finishing aluminum products includes a variety of types and methods of surface treatment. Therefore, it is very important for designers and architects to know:
- what types of aluminum finishes are used in industry
- what are the signs you need to identify them
- how to choose the right finishing.
To achieve a high quality finish in architectural aluminum, well-coordinated teamwork and cooperation of all participants is required:
- architect (designer)
- supplier of aluminum products and materials
- manufacturer of primary aluminum products
- aluminum finishing manufacturer
- construction works manufacturer.
The quality of the finishing of aluminum products is not solely the responsibility of one of them:
- Architect: Must understand the characteristics and limitations of the available finishes in aluminum in order to, so he can choose those, which are suitably suited for its purposes. Moreover, he must clearly formulate his requirements for the selected type of finish aluminum.
- Manufacturer (supplier) of aluminum products and manufacturer of finishing: must properly interpret the requirements of the architect (designer), apply the correct aluminum alloys and trace, so that all technological stages are completed, which are necessary to achieve the specified requirements for finished aluminum products.
- Construction contractor: must provide, so that at the construction site with all products, which have a vulnerable finish, treated with due care, and after their installation and installation, they were provided with proper protection against damage.
2 Finished aluminum
Base metals, which are used in construction and architecture are aluminum, copper, stainless steel and carbon steel. Compared to other metals, aluminum has the largest variety of possible finishes.. Almost all finishing technologies for copper, stainless steel and carbon steel are also used for aluminum, while some of its types are used only for aluminum.
It is known, what [1]:
- Most aluminum finishing technologies are not used by primary aluminum producers, and other specialized manufacturers or manufacturers of finished aluminum products.
- The only kind of finishing, which is typical only for primary aluminum producers, may be a kind of finishing "without additional processing", which corresponds to the English term “as fabricated”.
- At the same time, some primary manufacturers also supply aluminum products with additional finishes, for example, rolled aluminum sheets with organic or laminated coating.
- All other finishes are received by the aluminum product after, how it leaves its primary equipment: the rolling mill, extrusion press or foundry.
3 American Aluminum Association classification
3.1 Structure and notation
The American Aluminum Association (AA) has developed a detailed classification and designation of all industrially used types of aluminum finishes [1, 2].
All aluminum finishes fall into three main categories:
- Technical finishes (M)
- Chemical finishes (C)
- Coatings (A, R, V, E, L)
The category "Coatings" is further subdivided into subcategories:
- Anodic coatings (A)
- Organic coatings (R)
- Enamel coatings (V)
- Electrolytic and other metal coatings (E)
- Laminated flooring (L).
Each category and subcategory is identified by a separate letter. The letter may be followed by a two-digit number to indicate different options for this type of finish..
The "X" mark denotes existing and future options for this type of finish or treatment..
Finish designations can be used alone or in conjunction with other designations, to install a complete finishing system.
If only a two-digit letter is used in the designation of the anodic coating, then it means, that the type of preliminary preparation before anodizing is assigned by the manufacturer of the finish, taking into account the type of product and its end use [1].
3.2 Example of designation of finishing
An example of a typical finish for an interior decorative aluminum panel:
- AA-M42C21A34:
AA: American Aluminum Association
M42: Machined to a fine, matte surface with non-directional texture
C21: Etching to obtain a fine matte surface
A34: architectural anodizing, class II; electrolytic dyeing
Note:
The finishing manufacturer and the customer agree (on samples or in writing) the technology, which will be used for the M42 and C21 finishes
3.3 AA classification
3.3.1 Machining by cutting
- Without additional processing:
M10 - Characteristics not specified
M11 - High gloss as a result of the manufacturing process
M12 - Low gloss
M1X - Other variants "1X" (existing and future) - Polishing
M20 - characteristics not specified
M21 - Smooth, high gloss
M22 - High gloss
M2X - Other "2X" variants (existing and future) - Directional Texture:
M30 - Without specification of characteristics
M31 - Thin matte
M32 - Medium matting
M33 - Rough matting
M34 - Manual processing
M35 - Steel brushing
M3X - Other variants "3X" (existing and future)
- Non-directional texture:
M40 - No characteristics specified
M41 - Ultra-thin matting
M42 - Thin matte
M43 - Medium matting
M44 - Rough matting
M45 - Processing with fine shots
M46 - Medium shot
M47 - Coarse shot
M4X - Other "4X" variants (existing and future)
3.3.2 Chemical treatment (C)
- Cleaning without etching:
C10 - Characteristics not specified
C11 – Degreasing
C12 - Chemical cleaning with inhibition
C1X – Other options "1X" (existing and future)
- Etching:
C20 - Characteristics not specified
C21 - Thin matting
C22 - Medium matting
C23 - Coarse matting
C2X - Other "2X" options (existing and future) - Chemical polishing:
C30 - Characteristics not specified
C31 - High gloss
C32 - Diffusion polishing
C3X - Other "3X" variants (existing and future)
- Chemical conversion coatings
(Not applicable for subsequent anodizing):
C40 - Characteristics not specified
C41 - Acid chromate fluoride
C42 - Acid chromate-phosphate
C43 - Alkaline chromate
C4X - Other "4X" variants (existing and future)
3.3.3 Anodic coatings (A)
- General:
A10 - Characteristics not specified
A11 - Preparation for application of other coatings
A12 - Anodic coatings in chromic acid solutions
A13 - Solid, wear-resistant coatings
A1X - Other options "1X" (existing and future) - Decorative and protective (coatings with a thickness of at least 10 μm:
A21 - Colorless - Specified coating thickness
A22 - Integral staining - Specified coating thickness.
Coating color depends on alloy and process conditions
A23 - Impregnation paint - Specified coating thickness
A24 - Electrolytic painting - Specified coating thickness
A2X – Other "2X" options (existing and future)
- Architectural class II (coatings from 10 to 18 μm):
A31 - Colorless
A32 - Integral staining
A33 - Impregnation staining
A34 - Electrolytic staining
A3X - Other variants "3X" (existing and future)
- Architectural class I (coatings thick 18 μm and more):
A41 - Colorless
A42 - Integral staining
A43 - Impregnation staining
A44 - Electrolytic staining
A4X - Other "4X" variants (existing and future)
3.3.4 Electrolytic coatings (E)
E10 - Characteristics not specified
E1x - Other options "1X" (existing and future)
3.3.5 Organic coatings (R)
R10 - Characteristics not specified
R1X - Other options "1X" (existing and future)
3.3.6 Enamel coatings (V)
V10 - Characteristics not specified
V1X - Other variants "1X" (existing and future)
3.3.7 Laminated flooring (L)
L10 - Characteristics not specified
L1X - Other options "1X" (existing and future)
4 Detailing and further classification
Detailed consideration of features and a more detailed classification, as well as other classification systems for finishing aluminum materials and products can be found in the following documents:
- Mechanical processing [1]
- Chemical processing [1, 3]
- Anodic coatings [1, 3-5]
- Organic coatings [6, 7]
Sources:
- Metal Finishes Manual – National Association of Architectural Metal Manufacturers (США) – naamm.org – 2006
- https://www.anodizing.org/page/aluminum-association-designation
- DIN 17611 Anodized products made of aluminum and wrought aluminum alloys - technical delivery conditions
- Aluminum leaflet O 4 - Anodized aluminum for decorative purposes - 15. Edition
- QUALANOD Spec_ED 01.01.2021 – http://qualanod.net/
- QUALICOAT_Specifications_2021_MASTER_VERSION_V02 – https://qualicoat.net
- https://gsb-international.de/en/information/technical-information/
