In the metal finishing industry there are many different types of processes which give a range of enhanced properties to components. Companies involved in metal finishing may specialise in just one of these processes, or may be equipped to carry out most, or all.

Here we take a look at metal finishing, what the different processes are, and the regulations which govern them.

What is metal finishing?

The main purpose of metal finishing is to give enhanced properties to various substrates (the metal that is to be coated or finished). It can also be used to give decorative coatings to metals.

Metals used in engineering and manufacturing, often do not have the necessary strength, durability or resistance to outside factors needed for its application. To enable the metal to be used, a coating or finish is applied so that the metal’s properties are altered to give a better performance.

The finishing processes are used to give the following improvements:

· Improved appearance

· Improved adhesion

· Greater solderability

· Resistance to corrosion, chemicals, wear, extreme temperatures and tarnish

· Hardness

· Durability

· Electrical conductivity

· Removing of surface flaws and burrs

· Control of surface friction

The many uses of metal finishing

Metal finishing and surface coating techniques are used for many applications, from new technologies and processes to traditional manufacturing, where the surface of the metal is subjected to a number of harsh processes.

Sectors as wide ranging as automotive, aerospace, defence, power supply, electronics, petrochemical, medical, chemical and engineering, to name but a few, rely on products which have been subjected to the finishing process.

Types of metal finishes

There are several different ways to carry out metal finishing, some more commonly used than others. These include, but are not limited to:

· Electroplating – This process involves passing an electrical current between two electrodes (one, being the substrate that is to have the metal finish) through an electrolyte solution. The electrical current causes a chemical reaction that results in the atoms of the electrolyte being split up and deposited on the electrode. Therefore, if you wish to coat a substrate with silver, then the electrolyte would need to be made up of a silver-based solution. Electroplating can be carried out on a wide range of metals including, gold, silver, tin, copper, cadmium, nickel, platinum, zinc and lead

· Anodising – The process of anodising is much the same as electroplating, whereby an oxide film is formed on the substrate by passing an electrical current through an electrolytic solution. Aluminium is commonly used within anodising, while both magnesium and titanium can also be anodised.

· Electroless plating – this process involves applying a uniform layer(s) of a metal to a substrate without the need for an electrical charge. Nickel is often used for this process as it gives a uniform thickness on the substrate even on awkward shaped objects.

· Passivation – This process is used to improve the surface condition of stainless steel by dissolving any iron that has been deposited during manufacturing. This is achieved by placing the stainless steel into an acid solution to dissolve the residual iron and to form a thin oxide layer on the surface.

EU and UK regulations

Metal finishing and surface coating are covered by several pieces of European and UK legislation and directives. The many processes using chemicals and the disposal of any by-products are covered under various environmental regulations as well as health and safety laws. Information on the legislation and other guidelines for the metal finishing and surface coating industry can be found on the Surface Engineering Association’s (SEA) website.

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