Metal Finishing Specialists
Metal Colours Ltd -  Zinc Plating

Zinc Plating: Three automatic rack plants with a maximum process window of 3.6m x 1.5m x 0.7m. Two large automatic barrel process plants with 1.2m cylinders. The process solutions are alkaline non-cyanide based. Clear, Colour and Hexavalent Chrome Free passivation and topcoats are available. All plants have fully automated transporters with a high degree of process control, which includes automatic dosing of process chemicals and additives as well as process solution temperature and direct current control.

Benefits: Zinc is the process of choice for a cost effect method of achieving enhanced corrosion protection. It is also an ideal sub-surface for final finishing. [top]

Corrosion Protection: Corrosion protection is directly proportional to the electroplate thickness (3-30µm according to our client's specification). The principal protection is due to the zincs encasement of the item, which prevents contact with the environment. An important feature of zinc is it’s sacrificial property, which means that where the ferrous base of the item is exposed to humidity for example, the associated chemical reactions of corrosion will affect the zinc in preference to the steel. Zinc also provides outstanding metal distribution and uniform covering power. The coating is capable of accepting the environmentally friendly clear blue trivalent chromium passivate as well as yellow and olive drab finishes.

Wear Protection: Zinc plating bestows an increased surface hardness on the item with the finished hardness (100g HV) ranging between 80-150HV. Zinc is beneficial where items must retain their original appearance for many years. [top]

Corrosion Protection
  White-h Red-h
Clear Passivate 20 100
Yellow Passivate 70 150-200
Hexavalent chrome Free Thick Film 130 300
Olive Drab Passivate 150-200 250-360
Black Passivate 30-50 120-50
Above data relates to corrosion testing in accordance with ASTM B117 procedures, 5% neutral salt spray, and deposit thickness 8µm. Silicate post dips and lacquers can add 100-250h to the above values. Protection of steel substrates (red rust corrosion) is proportional to the deposit thickness.

Value Added Services: Zinc plating can be used as a final finish or as a base for post-treatments. Additional treatments can be applied to complement the primary finish such as clear or coloured lacquering, oil seals, wax silicate finishes, leach and seal systems or wax emulsions dosed with corrosion inhibitors. Post treatment applications can be applied for functional or aesthetic purposes. [top]

Metal Colours Ltd -  Zinc-Nickel Plating

Zinc-Nickel Plating: One automatic rack plant with a maximum process window of 3.6m x 0.9m x 1.1m. One large automatic barrel process plant with 1.2m cylinder. Both plants are operating an alkaline zinc-nickel process depositing 12-15% nickel.

Benefits: High zinc-nickel alloy provides an excellent level of corrosion protection, especially under arduous thermal conditions and also lessens the process of voluminous white corrosion deposits typical of conventional and low alloy zinc finishes. [top]

Post-Treatment: High nickel-zinc alloy can be post treated with Hexavalent Chrome Free Thick Film iridescent yellow, bright, blue, olive drab or clear passivate as well as a high quality colour fast black finish. Other post-treatments are available including sealants, lacquers and oils for specific requirements such as enhanced corrosion protection and high torque lubricity. [top]

Corrosion Protection: In general, corrosion protection is a function of the thickness of the deposit. The neutral salt spay test is used to assess the performance of a finish on a component. The test assesses the time before the onset of corrosion to the coating itself, the formation of white rust as well as the time before the onset of corrosion to the component substrate material, red rust. The tables below demonstrate some results from an ASTM B117 5% neutral salt spray test applied to a 5µm deposit. [top]

Neutral Salt Spray - hours to red (white) rust
Passivate type
Conventional zinc
High Nickel Alloy zinc
Clear 100 (6-24) 900 (240)
Iridescent Yellow 150-200 (72-96) 1500+ (1000)
Black 120-150 (72-96) 1500+ (500)
Hexavalent Chrome Free Thick Film 300 1500+
Conventional Zinc
Standard Zinc Alloy
High Nickel Zinc Alloy
Nickel % Nil 5-8 12-15
Vickers hardness (100g) 90-130 200-250 400-500
Weldability Poor Good Good
Thermal stability Poor Good Excellent

Metal Colours Ltd -  Electrophoretic Paint

Electrophoretic Paint: An automatic electrophoretic paint (E-coat) plant with a process window of 1.5m x 0.9m x 0.3m and a maximum load capacity of 250Kg. E-coat offers high corrosion resistance coupled with an excellent aesthetic appearance which is fast becoming the coating of choice for the automotive industry.

Benefits: The principal benefit of electrophoretic paint is the uniform density of the finish across the whole part, even on complex shapes. The benefit of a uniform coating density is an important feature where colour consistency is required. E-coat is often applied where corrosion protection is required to satisfy warranty agreements. Electrophoretic paint is a low cost treatment that offers the opportunity for a quick turn around on large volumes. [top]

Technology: Electrophoretic paint (E-Coat) technology is particularly advantageous for the application of a uniform organic coating formed on fabricated metal components. Unlike sprayed or dipped coatings, an electrophoretic coating is of uniform thickness on even the most complex shapes, including the edges. The size of components and parts is not in itself limiting; motor vehicle manufacturers routinely coat car chassis and other parts for corrosion protection with electrophoretic paint. [top]

Quality: Electrophoretic paint coatings are free of sags, beads and runs. These coatings exhibit excellent salt spray and humidity resistance, high throwing power, good hardness and flexibility. [top]

Automotive: E-coat is commonly used through out the automotive industry where high corrosion resistance is required on sub frame components such as steering racks, suspension mounts, chassis fixtures and auxiliary attachments such as tow bars. [top]

Paint Process PPG POWERCRON Cationic epoxy coating-high build
Thickness 15-30 micron, according to specification
Hardness 2H minimum
Throwing Power 18-20cm (Ford Test)
Ductility Very Good
Cross Hatch Adhesion 95-100%
Colour Black
Gloss-60 degree 20-60%
Corrosion Protection Neutral salt spray resistance 1000 h plus
Film properties based on zinc phosphate pretreatment with chromate seal.

Metal Colours Ltd -  Powder Coating

Powder Coating: An automatic powder coating line offering a complimentary finish to our other surface treatment services.

Benefits: Powder coating is an ideal method of adding a colour or aesthetic coating to a zinc or zinc-nickel item. Thermosetting powders, having a wide field of use, are well established. Automated process plant and a powder utilisation in excess of 95% ensure that powder coatings offer a viable commercial option to conventional industrial liquid paints. A high gloss, decorative and, depending on polymer, corrosion resistant finish with excellent cover on sharp edges is obtained with powders. Semi-gloss, matt, metallic and textured finishes are also available. Areas of use include automotive components, point of sale equipment, garden tools, satellite dishes and audio speaker housings. [top]

Colour Charts: Click these links to see our colour charts: BS4800 - Pantone - RAL

Polyester Powder: Recommended for use on exterior fittings where high resistance to weathering is required, and suitable for products used at elevated temperatures due to its high resistance to yellowing.

Epoxy Polyester Powder: A high performance product, classified during manufacturing and recommended for use where good chemical and detergent resistance is needed. Combined also with excellent decorative appearance and ease of application, is the advantage of good colour stability. [top]

  Polyester Powder Epoxy Polyester Powder
Film thickness 50-70 microns 30-70 microns
Full gloss 85% + @ 60° 95% + @ 60°
Semi gloss 50-70% + @ 60°
Matt 25-35% + @ 60° 20-40% + @ 60°
Scratch BS 3900 E2 Pass 4kg
Impact BS 3900 E3 Pass 80 in/lbs BS 3900 E3 Pass 100 in/lbs
Humidity BS 3900 F9 No blistering after 1000 hours (zinc phosphated steel)
Salt Spray/ASTM B117 2-4mm creep after 1000 hours (zinc phosphated steel)
Heat Stability No yellowing on continuous exposure up to 130°C or intermittent exposure up to 140°C No yellowing on continuous exposure up to 110°C or intermittent exposure up to 130°C

Metal Colours Ltd -  Technical Services

Technical Services: Metal Colours Ltd operate a technical centre whose task it is to ensure high quality standards across all finishing operations. The technical centre is equipped with a range of analytical tools and reference material with which to monitor operating processes, optimise chemical process routines and liaise with customers regarding the most suitable finish for their components. [top]

Expertise: The Technical Centre is directed by an experienced professional chemist whose principal responsibility in conjunction with the Quality Manager, is the maintenance of the highest standard of quality for all clients' work. [top]

Technology: The Centre operates state of the art analytical technology, including x-ray fluorescence equipment for the determination of plated metal thickness and zinc alloy analysis, an atomic absorption spectrophotometer, and a potentiostat. The Centre is also responsible for the optimum process control of the plating, electrophoretic paint and powder coating plants and carries out non-destructive testing on behalf of clients. [top]

Salt Spray Testing: The Centre operates a full salt spray testing cabinet and carries out testing on behalf of clients in accordance with ASTM B117 for runs of up to 2000 hours. [top]

Metal Colours Ltd -  Environmental
Environmental: Metal finishing processes are subject to strict environmental control. Our purpose built plant uses the latest technology to limit particulate and chemical emissions to air and water. We have eliminated the use of trichloroethylene and cyanide in all our treatment processes. Plating operations are Part-B processes controlled by the local authority to which Metal Colours must demonstrate the use of best available technology to control pollution. We also satisfy all waste minimisation and IPPC requirements and are compliant with the End Of Life Vehicle Directive and the Waste Electrical and Electronic Equipment Directive. [top]


Metal Colours Ltd -  WEEE & RoHS Compliance

WEEE & RoHS Compliance: Metal Colours Ltd is WEEE & RoHS compliant and offer suitable alternatives for both Lead and Hexavalent Chromium compounds and do not operate any treatments that contain Polybrominated Biphenyls (PBB), Polybrominated Diphenyl Ether (PBDE), Mercury or Cadmium. If you have a requirement for a WEEE & RoHS compliant service or are unsure of your responsibilities, feel free to call and we will be happy to help.

We offer statements of compliance where required. [top]

Metal Colours Ltd -  Quality

Quality: Metal Colours Ltd hold current accreditations for ISO 9001 -general management practice and ISO 14001 - environmental management systems. Certification was awarded through Independent European Certification Ltd.

Certificates: You can view our certificates here: ISO9001, ISO14001

Customer Focus: Metal Colours Ltd is a technically competent, service focused and client-oriented company. We aim to continuously improve client satisfaction. Our marketing strategy is to develop partnership relationships with our clients and our technology suppliers. [top]

Metal Colours Ltd -  Logistics

Logistics: Metal Colours Ltd operate a fleet of three articulated lorries and one 12 tonne lorry which are available for regular delivery and pick up of clients components subject to commercial agreement. All our services offer a maximum five-day turn around. [top]


9 Cambridge Avenue, Trading Estate, Slough, Berkshire, SL1 4QG
Tel: 01753 526644 - Fax: 01753 692454 -
Zinc - Zinc/Nickel Plating - Electrophoretic Painting - Berkshire