Volvo STD 5741-103 Anodizing (Coating) of Aluminum

The standard "Volvo STD 5741-103 Anodizing (coating) of aluminum", developed by the Volvo car company, describes the general requirements for anodic oxide coatings on aluminum. This standard defines the characteristic properties of anodic oxide coatings on aluminum, lists test methods to check the characteristic properties, specifies minimum performance requirements, provides information on aluminum grades suitable for anodizing, and explains the importance of pretreatment to provide the required appearance or texture of the finished job.

This standard applies primarily to aluminium oxide coatings formed on aluminium by an electrolytic oxidation process in which the aluminium serves as the anode.

The following are outside the scope of this standard:

• Barrier layer type non-porous oxide coatings
• Oxide coatings designed solely to prepare the substrate for subsequent application of organic coatings or electroplating of metals
• “Hard anodized” coatings, used primarily for engineering purposes and where wear and tear resistance are primary properties

For the purposes of this standard, the following definitions apply:

• Aluminum: Aluminum and aluminum-based alloys.
• Anodized aluminum: Aluminum with an anodized coating. It is produced by an electrolytic oxidation process in which the surface of the aluminum is converted to a coating, usually an oxide, that has protective, decorative or functional properties.
• Color coated aluminum: Aluminum with an anodic oxide coating that is colored with absorbent molds.
• Integrated color coating: Coating of aluminum using a suitable (usually organic acid-based) electrolyte that produces a colored oxide coating during the coating process on certain aluminum alloys.
• Electrolytic coloring: Coloring of the anodic oxide coating by electrolytic deposition of metals or metal oxides in the porous structure.
• Bright anodized aluminum: Anodized aluminum with high specular reflection as its primary characteristic.
• Decorative coating: A coating in which a decorative surface with a uniform or aesthetically pleasing appearance is the primary feature.
• Architectural coating: A coating of an architectural surface to be used in permanent, exterior and static situations where both appearance and longevity are important.
• Sealing: It is a hydration process of anodic oxide coatings applied after coating on aluminum to reduce porosity or the absorption capacity of the coating.
• Critical surface: The portion of a part that is or will be coated with a coating and where the coating is essential for serviceability or appearance.
• Measurement area: The area of ​​the significant surface over which a single measurement is made. For the following methods, the measurement area is defined as follows:
  • For analytical methods, the area where the coating is removed
  • For the anodic dissolution method, the area enclosed by the sealing ring of the cell
  • For the microscopic method, where a single measurement is made
  • For non-destructive methods, the probe area or the area affecting the reading.

Most aluminum can be coated in any of its forms, but the results vary greatly in appearance, color, maximum coating thickness, reflectivity, wear resistance, corrosion resistance, and conductivity. The protective value of the coating is excellent on many aluminums produced for general engineering purposes, but special grades of aluminum have been produced for uniformity of appearance or other special effects (e.g., shiny finish) in which close control of chemical composition and metallurgical practices are combined with high standards of surface quality and specific manufacturing procedures to provide a guaranteed response to anodizing. These are not easily classified because companies have developed their product lines to meet the needs of specific industries or customers, and there is no clear dividing line between the various categories.

The grades listed below are provided for general guidance and are based on the end use of the aluminium:

• Semi-finished products in the architectural quality class have a fairly uniform appearance after coating when viewed from a distance of at least 3 m. After coating, some differences in appearance and color can be expected between different batches of the same material and between different forms of the same material. Sometimes, when examined closely or from certain viewing angles, it is possible to observe differences in gloss, banding, streaking and other visual defects. These do not affect the quality of the coating.
• Semi-finished products in the decorative quality class have a particularly homogeneous appearance when viewed from a distance of 0,5 m. The coating can be matt, glossy or semi-diffused depending on the material and the anodizing process, but freedom from defects is guaranteed.
• Bright anodizing grade materials are typically based on high purity (99,7 percent) ingot metal or very high purity (99,99 percent) aluminum. Special mechanical, chemical, or electrochemical treatments may be used to achieve a highly polished or mirror-like finish after coating.
• Many grades of aluminum fall into the general engineering grade. It can be molded to provide a continuous coating with good protective value. However, there is no guarantee of appearance.

Among the numerous testing, measurement, analysis and evaluation studies that our organization has carried out for businesses in various sectors, it also provides testing services defined in the “Volvo STD 5741-103 Anodizing (coating) of aluminum” standard with its trained and expert staff and advanced technological equipment.