Electroplating and Anodising

Electroplating
Electroplating is the process of coating a metal, often for aesthetics or protection against corrotion.

The metal object to be elctroplated is placed on a negatively charged dipping rack. This runs a negative current through the metal object allowing positively charged bathing solutions to stick to the base metal therefore plating them.

The positive charge of the bathes come from a cathode submersed in the bath allowing electrical current to run through the metal rich solution. (the metal particle carrying the charge). The base metal acts as the anode to which the two opposing charges attract one another and therefore builds up a layer on the surfaces of the base metal.

Typically the most common electroplating metal is chromium. But other include copper, tin and zinc (Galvenising)

 

 

 

 



Multiple baths are needed to plate a metal as the metal first needs to be cleaned of any impurities. The thickness of the plating metal depends on the amount of time it is bathed for and the addition of any Strikes/Flash's used in the solution.

 

 

Anodising

Anodising is similar to electroplating where the negatively charged base metal is subersed in a bath with a positive charged cathode (lead) within it.

The anodising method uses metals similar to the way they are used in electroplating but you can add dyes to the solution as the surfaces of the base metal are often very pourous. These pour in the metal allow the base metal to accept the dye.
Therefore once anodising you need to complete the process with the use of a laquer.

Ferrous Metals

Iron

Iron (Ferrite) is extracted from its ore by using heat. During the extraction process the impurities are removed from the furnish leaving a greyish metal once cooled. Iron is rarely used without the addition of carbon thus creating Steel which is much stronger.

Steel

A combination of Iron and Carbon, Steel can have great toughness depending on the carbon content of the alloy. The higher the carbon content the more tough the steel is but the more brittle. Similarly the less carbon content the less tough the steel is.

By adding another metal to the steel alloy enables more specific properties to be enhanced for example zinc coating makes it resistant to corrosion.

Carbon

Carbon is used in many materials to add properties of strength and ductility. Organic materials that carbon is found in include diamond and coal. The amount of carbon used in a steel alloy varies the strength and hardness; however the addition of too much carbon can have the opposite effect and cause brittleness to the material.

Iron and Carbon

Iron is generally a soft and ductile material, these properties do not make a a very useful material for commercial uses. When carbon is added to Iron the characteristics of the new material (Steel) changes and therefore resulting in a wide range of specific properties.

An increase in the amount of Carbon will result in:

The material becoming harder

Toughness reduces, con become brittle

High Carbon Steel and Medium Carbon Steel can be heat treated to increase Strength and Hardness of the material.

Heat Treatments

Annealing

Quenching

Tempering