What is Powder Coating?
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Powder coating is a widely used method of applying a decorative and functional paint finish to a wide variety of products including white goods, leisure goods, architectural cladding, vehicle trim, electronic enclosures, railway interiors and office furniture.
The powder in question is made up of finely ground resins and pigments and is most commonly applied through an electrostatic spray gun. The gun applies a charge to the powder as it is sprayed and this causes the powder to cling to the electrically grounded component.
After the powder has been applied to the component, it must be transformed into a continuous film by heating (typically at temperatures between 160 C to 220 C.)
Advantages of powder coating
- Powder coating tends to be tougher more flexible coating and less liable to chip or peel than a conventional wet paint.
- Unlike many wet paints, powder coatings have no VOC content
- Powder coatings will give a uniform appearance over a large area and not exhibit the characteristic evidence of the direction of application found with wet paints.
Powder Coating Colours
The colour standards typically used for powder coating within the UK are: RAL, BS 4800, BS 381C, NCS and Pantone.
RAL shades
In 1925, the private sector and the German government of that time founded the "Reichsausschuss für Lieferbedingungen" - RAL - (Committee of the German Reich for Terms and Conditions of Sale). In 1927 this body created the first RAL colour chart; the RAL 840 colour scale containing 40 colours.
The RAL colour standard now contains approximately 2000 shades but it is a small sub section of RAL colours (approximately 200 shades) designated RAL CLASSIC which are commonly used in powder coating in the UK.
Each RAL CLASSIC shade is designated by a 4 digit numerical code e.g. RAL 6005. The RAL shades are organised in groups of colours as follows:
Shades beginning in 1 – beige/yellow/ivory
Shades beginning in 2 – orange
Shades beginning in 3 – red/pink
Shades beginning in 4 – purple/lilac/violet
Shades beginning in 5 - blue
Shades beginning in 6 - green/olive
Shades beginning in 7 - grey
Shades beginning in 8 - brown
Shades beginning in 9 – white/black (plus 9006 & 9007 which are different to the other classic shades and can vary considerably between manufactures.)
For more information see the RAL website
RAL 9006 & RAL9007
The colour reference standards used in powder coating (e.g. RAL, NCS etc) can be reproduced by powder manufacturers within established tolerances giving good agreement between different manufacturers. This is not so with RAL 9006 and RAL 9007 where wide variations in appearance occur between powder manufacturers. These colours originate from the corrosion protection program of the German state railway. They were used for corrosion protection of steelwork and rolling stock and were never intended to be used for decorative purposes. RAL 9006 is essentially produced using aluminium particles, and RAL 9007 with iron oxide in a layered structure with small amounts of aluminium powder. These colours were registered with RAL to enable the railway to use them as references when placing orders but their inclusion has led to misunderstandings. Recently metallic colours have become popular for all sorts of architectural uses (window frames, door frames, cladding etc) and RAL 9006 and RAL 9007 have been specified even though there is no uniform finish in existence for the standards.
British Standard Shades
There are two sets of British Standard shades used for powder coating; they are: 'BS 4800:1989 - Schedule of paint colours for building purposes' These shades are generally more widely used than 381C and as the British Standard title suggests they are designed for architectural and construction industries. Each shade within the standard has has a 5 digit code made up of two numbers, a letter and two more numbers e.g. 10C31. The other British Standard Colour is 'BS 381C:1996 - Specification for colours for identification, coding and special purposes'. These shades are designated by a 3 digit numerical code e.g. 697.
NCS Shades
This NCS (Natural Colour System) standard has its origin in Sweden in the 1920's. This 'visual colour system' is based on ideas taken from "Das natürliche System der Farbempfindungen" published by the German physiologist Ewald Hering in 1874. The NCS system is an attempt to create a visually descriptive colour system. Colours in the NCS are designated by an 8 digit alpha numerical code defining darkness, saturation and hue. The first 4 digits specify darkness and saturation; the second 4 digit group refer to hue. For example: 3050 Y80R designates 30% darkness, 50% saturation, 20% yellow and 80% red. The Scandinavian Colour Institute as it is now known is responsible for and has the rights to the NCS system. For more information visit the NCS website www.ncscolour.com
Pantone shades
The Pantone system is widely used within the graphic design, printing, publishing, textile and plastics industries. It is sometimes specified for powder coating especially where a sign or piece of architecture is required to match a company logo or corporate colours. The Pantone system was created in 1963 by Lawrence Herbert in order to identify and match colours for the graphic arts community. As the colour spectrum is seen and interpreted differently by each individual, Pantone produced a book of standardized colours in a fan format. For more details go to: www.pantone.com
