Materials

Mild steel will corrode if un-treated and is usually used where the subsequent the treatment is zinc plating.

Zinc plating will render a part corrosion resistant and ‘passivation’ will colour it clear, yellow or black to suit requirements. Clear passivation will add about 30% to the cost, yellow passivation about 40% and black passivation about 100% .

Mild steel is easily TIG, MIG or spot welded. 

Mild steel (where it has been zinc plated) is commonly used for general purpose outdoor use such as cabinets.

Galvanisation involves passing mild steel sheet through a molten bath of zinc (hot dipping) as part of the manufacturing process rendering the sheet corrosion resistant. Its appearance is bright spangly grey and the surface is non-pourous, easily wiped and resistant to marking from oil, finger prints and other contaminants.

It has the same strength and weight as mild steel and is about 7% more expensive.

The material is readily welded using spot welding or MIG/TIG welding but if MIG/TIG welding is used, unpleasant fumes are released which must be extracted. Processes such as punching, shearing, welding and dressing expose edges which spoils the corrosion resistance and further finishing such as painting may then be required.

Galvanised sheet is commonly used for the internal parts of electronic enclosure.

Zintec is the trade name given to cold rolled and coiled mild steel sheet that has been electrolytically coated with a thin layer of zinc as part of the manufacturing process. Its appearance is dull grey and it has a porous surface which is easily marked by oil, finger prints and other contaminants.

It has the same strength and weight as mild steel and is about 7% more expensive. 

Zintec is readily welded using spot welding or MIG/TIG welding. Processes such as punching, shearing, welding and dressing expose edges which spoils the corrosion resistance and further finishing such as painting may then be required.

Zintec is a good ‘undercoat’ for powder coating or wet spray painting and is commonly used for internal and external enclosures.

Aluzinc is mild steel sheet with a high quality zinc and aluminium coating which is very corrossion resistent. It has the same strength and weight as mild steel but is about twice the price. It has an attractive semi-shiny mottled grey finish.

Aluzinc is readily welded using spot welding or MIG/TIG welding. Processes such as punching, shearing, welding and dressing expose edges which spoils the corrosion resistance and further finishing such as painting may then be required.

Because the natural finish is attractive and very corrosion resistant, it is often used for outdoor products such as flashings and garage doors.

Stainless steel has twice the strength of mild steel, is much harder, weighs the same and is about 4 times the price. It requires no added corrosion protection and is available in a number of surface finishes, for example:

2B – semi-reflective smooth grey sheen
BA – bright-annealed reflective surface
Grained – direction brushing with grit belts to various degrees of polish

The material is readily welded using spot welding or MIG/TIG welding and neither welding nor dressing will spoil its corrosion resistance. After welding and dressing, the surface is often grained or polished to achieve a consistent surface finish.

Grade 304 is used for general purpose applications and Grade 316 is used where hygene matters as in food processing (so called surgical steel) and in highly corrosive marine environments.

The extra cost of stainless steel offsets the cost of finishes such as zinc plating and painting and is worth considering where long term corrosion resistance is important.

The material is naturally attractive, hard, strong and used in instruments, cabinets, as decorative cladding and in structural applications.

The hardness of the material makes it hard to work with hand tools and stainless steel can be prone to greasy marks if handled.

Aluminium, (depending on the grade) is about 0.75 times the strength of mild steel, about 30% of the weight and about the same price. This makes it an attractive choice for many applications.

Aluminium ‘self-corrodes’ resulting in white pitting which leaves black marks when handled. For this reason, aluminium parts are often Anodised or Alochromed to stop corrosion.

Anodising stabilises the surface with a porous film which can be clear or dyed in colours such as red, yellow or blue to achieve a corrosion resistant, decorative finish.

Alochrome is a yellow coating which stops corrosion, makes parts pleasant to handle and provides a good undercoat for painting. Alochrome must not come in contact with food stuffs.

Aluminium is readily welded using MIG/TIG welding and neither welding nor dressing will spoil its properties. After welding and dressing, the surface is often grained to achieve a uniform surface finish. Spot welding aluminium requires very high powered equipment which we have in GW Engineering.

Grade 5251 is easy cut and folded, has about 0.75% the strength of mild steel and is very corrosion resistant.

Grade 1050 is similar to Grade 5251 but less strong, less corrosion resistant but has an attractive shiny surface. Both Grades are about the same price.

Aluminium is widely used where weight saving and strength are important particularly for the internal and external parts of mobile electronic equipment.

Copper is about 30% as strong as mild steel, slightly heavier and about 7 times the price.

Its high electrical conductivity means it is generally used for making electrical conductors such as busbars.