Metal Finishes

Finishes for metals

Cellulose and acrylic paints

Paints provide colour and sometimes a textured finish to metals.

They can also provide a barrier against corrosion for metals such as Steel and Iron.

The surface of the metal must be cleaned, de-greased and primed for the paint to adhere to the surface properly.

To get a full, rich colour an undercoat is often applied before the colour and, in the case of cars and other shiny products, a clear lacquer may be applied over the paint layer.

Electroplating

This involves using a metal to coat a (usually) cheaper metal to provide a protective layer and enhance the aesthetic qualities of the material.

For example, teapots can be silver plated and cheaper jewellery can be gold plated.

The metal product is submerged in a solution containing tiny particles of the plating metal. When the current is applied, the product attracts the donor metal and the product is electroplated.

Polymer dip coating

This is used on a variety of products such as wire coat hangars and outdoor equipment.

The metal is heated then the hot product is dipped into a tank of fine polymer powder which has air blown into it to ensure even distribution of the powder.

The hot metal melts the powder giving a tight fitting and even polymer finish.

Metal dip coating

Metal can also be dipped into other metals for coating.

In this case the product is dipped into a tank of molten plating metal. This process is often used for inexpensive metals such as low carbon steels, primarily to provide a barrier against corrosion.

Products can be Tin plated (food cans) up to car bodies.

Galvanizing

Using a Zinc plating is known as Galvanizing. It is used to produce car bodies, buckets, screws, hinges and much more. The Zinc coating provides a barrier to the metal underneath (usually mild steel) and prevents rusting.

Powder coating

This process gives a much better finish than dip coating.

A negatively charged product is sprayed with positively charged polymer powder so it sticks to it like a fine dust.

It then passes through an oven which bakes the fine layer of powder into an even coat of polymer. Used to coat chair and table legs as well as many domestic metal products such as fridges and washing machines.

Varnishing

Metal varnishing is a method used to provide a clear surface finish to metals, and it will also provide some resistance to corrosion.

They would be applied exactly the same as a paint or spray. Varnish is effectively paint without any pigment leaving it completely clear. A clear lacquer could also be used for a finer finish.

Sealants

Metal sealants are tough polymer based sealant coatings that protect polished surfaces from decay and tarnishing. Silicon based sealants are often used in the automotive industries as an additional bodywork barrier against weathering and rust. It is generally applied with a cloth or machine pad to produce a film that is then left to cure for 15 mins, before being 'buffed' to a shine.

Preservatives

Metal preservatives can provide temporary in-process or final post-processing protection for metal surfaces. They are ideal for moulds and dies to prevent fingerprints showing on surfaces. They can be applied with a cloth, spray or via immersion.

anodising

This is a finishing process commonly used for Aluminium products to enhance the natural oxide layer and provides increased hardness and toughness.

It is similar to electroplating but penetrates the surface of the material which can then be finished with a lacquer or varnish to further protect the finish. Many Apple products are annealed, as are carabiners.

Cathodic protection

All metals have a natural voltage and when two different metals are joined together there is an electrical current. If water is present at the joint it results in the formation of an electrochemical cell and one of the metals will corrode.

Cathodic protection is a method used to control the rate of corrosion. The main use is to protect steel structures buried in soil or immersed in water such as pipelines, ships and offshore platforms.

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