Aluminum alloys are divided into two major categories:
wrought and casting alloys. A further differentiation for
each category is based primary on mechanism of property
development. Many alloys respond to thermal treatment based
on phase solubility. These treatments include solution heat
treatment, quenching and precipitation, or age hardening.
In order to improve surface properties of final products,
such as wear resistance, corrosion resistance, reflectivity
etc., different types of surface treatment were designed.
All of them are divided into several groups, such as
electrochemical treatments, chemical treatments and
coatings. In this article their terms and definitions will
Electrochemical brightening: Electrochemical treatment
to improve the optical reflectivity of a surface.
Electropolishing: Polishing of a metal surface
by making it anodic in an appropriate electrolyte.
Anodized metal Metal with an anodic coating, produced
by an electrolytic oxidation process in which the metal is
converted to a mainly oxide coating having protective,
decorative or functional properties.
Clear anodized metal: Metal with a substantially
colorless, translucent anodic oxidation coating.
Color anodized metal: Anodized metal colored either
during anodizing or by subsequent coloring processes.
Integral color anodized metal: Metal that has been
anodized using an appropriate (usually organic acid based)
electrolyte which produces a colored coating during the
anodizing process itself.
Electrolytically colored anodized metal: Metal with an
anodic oxidation coating that has been colored by the
electrolytic deposition of a metal or metal oxide into the
Dyed anodized metal: Metal with an anodic oxidation
coating colored by absorption of dye-stuff or pigments into
the pore structure.
Combination color anodized metal: Metal with an anodic
oxidation coating that is colored by electrolytic coloring or
produced by integral color anodizing followed by absorption
Interference color anodized metal: Metal with an
anodic oxidation coating colored by means of optical
Bright anodized metal: Anodized metal with a high
specular reflectance as the primary characteristic.
Protective anodizing: Anodizing where protection
against corrosion or wear is the primary characteristic and
appearance is secondary or of no importance.
Decorative anodizing: Anodizing where a decorative
finish with a uniform or a esthetically pleasing appearance
is the primary characteristic.
Architectural anodizing: Anodizing to produce an
architectural finish to be used in permanent, exterior and
static situations where both appearance and long life are
Hard anodized metal: Anodized metal on which the
anodic oxidation coating has been produced with wear and/or
abrasion resistance as the primary characteristic.
Sealing: Treatment of anodic oxidation coatings on
metal to reduce porosity and the absorption capacity of the
coating by hydrothermal processes carried out after
Cold impregnation: Treatment of anodic
oxidation coatings on metal to plug the pores and reduce the
absorption capacity of the coating by chemical processes
carried out at low temperatures after anodizing.
Significant surface: The part of the product covered
or to be covered by the coating and for which the coating is
essential for serviceability and/or appearance.
Chemical brightening: Chemical treatment to
improve the optical reflectivity of a surface.
Chemical polishing: Polishing of a metal surface
by immersion in a solution of chemical reagents.
Degreasing: Removal of oil or grease, usually by
a suitable organic solvent or an aqueous detergent.
Etching: Roughening of the surface of a metal by
overall or selective dissolution in acid or caustic media.
Pickling: Removal of a thin surface layer of a metal
by chemical action, mainly by treatment in a caustic
Coil coating: Continuous coating of a metal strip.
Coating (organic): Method in which a coating material
is applied on a metallic substrate. This process includes
cleaning and chemical pre-treatment and either:
- one-side or two-side, single or multiple application of
liquid or powder coating materials which are subsequently
- laminating with plastic films.
Backing coat: Single coating of any type with no
particular requirements for appearance, malleability,
corrosion protection, etc. usually on the reverse side of
the coated product.
Chemical conversion coating: Treatment of a metal with
chemical solutions by dipping or spraying to build up an
oxide film containing chromates or phosphates.
Priming: Application of a priming paint often
pigmented with a corrosion inhibitor such as zinc chromate,
after suitable pretreatment.
Pretreatment priming: Application of a solution
containing a resin, a chromate and an acid, which is allowed
to dry on and provide the key for subsequent painting.
Single coat system: Single coating either with
requirements on appearance, malleability, corrosion
protection, subsequent painting, etc., or as a primer with
special properties regarding adhesion and corrosion
protection for post-painting applications.
Multiple coat system: System comprising a primer or a
base coat, possibly intermediate coat(s), and a top coat with
particular requirements on appearance, malleability,
corrosion protection, etc.
Organic coating: Dry paint film of the coated product
or the organic film metal laminate.
Film coating: Organic film applied to a substrate to
which an adhesive and, if appropriate, a primer has been
Lacquering: Coating with a formulation based on a
dissolved material which forms a transparent layer primarily
after drying by evaporation of the solvent.
Painting: Coating with a non-transparent formulation
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