Aluminium anodisingAluminium powder coating

Architectural Aluminium finishing

All about architectural  finishing aluminum in the building industry: types, signs + how to choose the best finish.

1 Why is it useful to know?

Architectural aluminium finished 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 aluminium finishes are used in industry
  • what are the signs you need to identify them
  • how to choose the right aluminium finishing.

To achieve a high quality finish in architectural aluminium, well-coordinated teamwork and cooperation of all participants is required:

  • architect (designer)
  • supplier of aluminium products and materials
  • manufacturer of primary aluminium products
  • aluminium finishing manufacturer
  • construction works manufacturer.

The quality of the finishing of aluminium products is not solely the responsibility of one of them:

  • Architect: Must understand the characteristics and limitations of the available finishes in aluminium 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 aluminium products and manufacturer of finishing: must properly interpret the requirements of the architect (designer), apply the correct aluminium alloys and trace, so that all technological stages are completed, which are necessary to achieve the specified requirements for finished aluminium 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 Archtectural aluminium finishing

Base metals, which are used in construction and architecture are aluminium, copper, stainless steel and carbon steel. Compared to other metals, aluminium has the largest variety of possible finishes. Almost all finishing technologies for copper, stainless steel and carbon steel are also used for aluminium, while some of its types are used only for aluminium.

It is known, what [1]:

  • Most aluminium finishing technologies are not used by primary aluminium 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 aluminium products with additional finishes, for example, rolled aluminium 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 aluminium finishes [1, 2].

All aluminium finishes fall into three main categories:

  • Machining (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 aluminium 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

  • 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:

  • Machining [1]
  • Chemical processing [1, 3]
  • Anodic coatings [1, 3-5]
  • Organic coatings [6, 7]

Sources:

  1. Metal Finishes Manual – National Association of Architectural Metal Manufacturers (США) – naamm.org – 2006
  2. https://www.anodizing.org/page/aluminum-association-designation
  3. DIN 17611 Anodish oxidierte Erzeugnwsse aus Aluminium und Aluminium-Knetlegirungen – Technische Lieferbedigungen
  4. Aliminium-merkblatt O 4 – Anodisch oxidiertes Aluminium fur decorative Zwecke – 15. Auflage
  5. QUALANOD Spec_ED 01.01.2021 – http://qualanod.net/
  6. QUALICOAT_Specifications_2021_MASTER_VERSION_V02 – https://qualicoat.net
  7. https://gsb-international.de/en/information/technical-information/