Metals

Steel refers to any iron-carbon alloy, although steels usually contain other elements as well. In New Zealand steel is made by BHP NZ at Glenbrook, where about 90% of New Zealand's annual steel requirements are produced. READ MORE...

Steel in this form is usually processed further before being sold to customers. This generally involves rolling it into thinner sheets (and sometimes forming it into tubes). This steel is now conveniently shaped, but is prone to rusting so for applications where it is exposed to the weather it is often galvanised (and sometimes painted as well) to prevent corrosion. READ MORE...

Every year in New Zealand significant quantities of scrap metal are produced both as industrial off-cuts and when metal products wear out. As there are no economically viable sources of essential metals in New Zealand, it is often more sensible to recycle this metal than to import fresh stock. This is especially true of non-ferrous metal as it is more expensive than iron to buy, and thus recycling is usually a cheaper option. READ MORE...

Aluminium is a light, conductive, corrosion resistant metal with a strong affinity for oxygen. This combination of properties have made it a widely used material, with applications in the aerospace, architectural construction and marine industries, as well as many domestic uses. It is only over the last century, however, that it has been possible to economically refine aluminium, due to the enormous amount of energy needed to electrolyse its oxide. READ MORE...

Anodising is a process for producing decorative and protective films on articles made of aluminium and its alloys. The article is made the anode of an electolytic cell with aqueous sulfuric acid as electrolyte where the following overall oxidation reaction occurs.

2Al + 3H₂O → Al₂O₃ + 6H₊ + 6e₋

A dense even layer of oxide about 0.08 µm thick is formed rapidly, followed much more slowly with a more porous layer up to 25 µm thick. READ MORE...

Silver mirroring is a process that was once carried out widely in New Zealand, and is still used to a small extent - particularly for restoring antique mirrors. It involves the plating of glass with a thin layer of silver, and the protection of this layer, and is carried out in a three or four step process depending on the method used. READ MORE...

Electroplating is the application of a metal coating to a metallic or other conducting surface by an electrochemical process. The article to be plated (the work) is made the cathode (negative electrode) of an electrolysis cell through which a direct electric current is passesd. The article is immersed in an aqueous solution (the bath) containing the required metal in an oxidised form, either as an aquated cation or as a complex ion. READ MORE...

Metal equipment must be cleaned from time to time to prevent damage and maintain efficiency of operation. The chemical cleaning of metals has a number of advantages over mechanical cleaning methods. The greatest of these are that the metal equipment to be cleaned doesn't need to be dismantled and reassembled, and the cleaning doesn't damage the equipment, leaving areas that are more vulnerable to corrosion than before. READ MORE...

Gold is well known as a rare and precious metal which is very valuable and is used to make jewellery. Almost as much gold is used in the electronics industry because it can easily be molded or drawn out into very fine wires, is resistant to corrosion and conducts electricity almost as well as silver. READ MORE...

Two methods of combating corrosion which are widely used in New Zealand are cathodic protection and chemical inhibitors. Both methods depend on controlling the charge on the metal surface, and this can be monitored by measuring the potential of the metal. READ MORE...