Page 16 - CFCM May-June 2021_Neat

CASF NEWS

well as improving the corrosion protection of the part, as in automo- shoes as a novelty finish, to protecting components in the mission to
tive bright trim or bathroom and kitchen fixtures or architectural an- Mars and everything in-between. For example, most of the bright
odizing. A summary of the most common types of surface finishes is trim on the exterior of automobiles is a multilayer of copper, several
given below. different types of nickel then a chromium cap layer, all over a plastic
resin mixture of ABS and polycarbonate. Almost all the under-hood
Anodizing: Anodizing is the process whereby the aluminum fasteners are now of a zinc-nickel alloy that will outlast the vehicle;
surface is converted to a thick, nano-porous aluminum oxide film. the shock absorbers are coated with hard chromium to vastly
The anodizing process improves the decorative, durability, and improve their wear resistance. The bumpers and running boards on
corrosion resistant features of the surface. Several metals can be today’s vehicles are multilayer nickel and chromium and will also
anodized, including magnesium and titanium but it’s mostly outlast the vehicle they are mounted on – a very long way from the
commonly aluminum. rusty, peeling bumpers of 40 years ago!
In the anodizing process, metal oxide is not applied to the surface
as with paint or plating but is fully integrated with the Electropolishing: Electropolishing is a process that uses a DC
underlying metal substrate so it cannot chip or peel. An anodized electric current to preferentially remove the high points on a rough
surface can be treated with secondary processes like coloring, metallic surface by levelling out micro imperfections and polishing
sealing and various topcoats for exterior OEM automotive applica- lines on the surface. In some cases, its main function is to impart
tions such as roof rails, window trim and, for example, all the bright gloss or improve lustre.
trim you see on the outside of a Tesla! Electropolishing has many applications in the metal finishing
Anodizing is used in very many applications and is becoming industry. Some of these include washing machine drums and
ever more popular. Some common ones include building exteriors surgical devices.
(such as storefronts, curtain walls, and other architectural uses),
appliances, furniture, automotive parts, boats, and others. Etching: Etching is the process of using strong acid or mixture of
acids to cut into a metal surface to create a design or impart a
uniform etched surface for further processing. Chemicals are used
with a template to create the design needed.
Etching is typically used in any process where decorative features
or patterns are needed. It is, as well, an important process in printed
circuit board manufacturing where a film is placed over a copper
laminated board and the exposed copper is etched off leaving the
circuit design behind for further processing.

E-coating: E-coating is the process whereby a metal part is
immersed in a solution containing a conductive paint emulsion. An
electric voltage is applied to the part causing the paint emulsion to
electrolytically deposit onto the part. This process results in nearly
100 percent encapsulation of the part with the paint layer. The e-
coat process has resulted in a significant increase in the lifetime of
metal parts and is used extensively in the OEM automotive arena,
but is also used in other industrial applications where 100 percent
coverage of the metal part is needed to prevent or minimize
Antiquing: Antiquing refers to the process whereby the object’s corrosion.
surface features are altered to make it appear to be an older object.
This can be accomplished in a number of ways including surface Hot-dip Galvanizing: Hot-dip galvanizing is the process of coating
finishing techniques. It normally consists of glaze or a thin layer of a metal substrate with another metal, usually zinc, by immersing
coating over a base finish. In the surface finishing industry, the the part in a molten bath of the metal. The thick metal layer forms a
object would normally be metallic, and an oxide film would be strong surface which prevents corrosion of the underlying metal
developed on the surface, then buff or brush relieved to create the substrate for many years. Hot-dip galvanizing is widely used where
appearance of age. corrosion protection of steel or iron is needed, and the zinc is
generally sacrificial to the underlying base metal thereby greatly
Electroplating: Electroplating of metal and certain resin enhancing the corrosion protection of the base material.
substrates, with the exception of paint, forms by far the largest Hot-dip galvanized objects are used in many applications. One of
subsection of the surface finishing industry globally. It is a process its important applications is in making steel frames and components
that uses a direct current (DC) power source to coat the substrate for steel frame buildings but also most highway light poles and
with a thin metal coating. Electroplating is used for a vast range of crash barriers are galvanized, as well as transport truck trailer
finishes, end uses and functions, all the way from coating baby chassis, and more.
16 CANADIAN FINISHING & COATINGS MANUFACTURING MAY/JUNE 2021