Information about the metal industry

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Treating the surfaces of metals The surface treatment of and by metals dates back to early man using gold decoratively before 4000 BC. Gold and silver plating (including their deposit from amalgams) was well-known by the 13th century AD, and tin plating of iron was carried out in Bohemia in 1200 AD. In the mid-19th century, the electrodeposition of metals was discovered enabling new possibilities, which are still being extended.

The surface properties of metals are typically changed for:

  • decoration and/or reflectivity
  • improved hardness (to maintain cutting edges and resistance to damage and wear)
  • prevention of corrosion.

Currently, the main areas of application are: automotive and transportation, packaging, building and construction (for more information, see Section 1.1). Two further commercial areas of application have emerged since the 1960s:

  • in microelectronics, especially with the advent of telecommunications and microprocessor controls in many common appliances. These demand mass-produced components with high conductivity capable of carrying very small electrical currents. This is achieved by applying precious metal plating on cheaper substrates
  • in printing, where aluminium is usually the substrate of choice for lithographic plates. The aluminium is first treated by electrochemical graining and anodic oxidation (anodising) prior to photosensitive treatments.

Treating the surfaces of plastics Plastics are now widely used in their own right and not only to replace metals. However, although they can be easily formed, may be flexible or rigid, and are corrosion-resistant and insulating, they lack other desirable properties. This has led to demands to change the surface properties of these new materials for:

  • decoration, to achieve a high value, metal-like appearance similar to gold, brass, and chromium
  • reflectivity, similar to chromium
  • durability, as plastics are generally softer than metals
  • electrical conductivity, usually in selected areas.

These requirements are met by depositing layers of metals on the surface of the plastic. Printed circuit boards are a specific case, where intricate electronic circuits are manufactured using metals on the surface of a plastic – usually resin or glass fibre board but also plastic films. A complicated series of processes removes and adds successive layers of metals as circuits to connect small holes. The inside surface of these holes are also coated with metal during the processes to enable electronic components to be subsequently soldered into them.

1.1 Industries using surface treatments

The surface treatment of metals and plastics does not itself form a distinct vertical industry sector. Surface treatments do not create products; they change the surface properties of previously formed components or products for subsequent use. Printed circuit boards might be considered products but are components manufactured for use in other products, and are made by a considerable number of interdependent manufacturing stages. The surface treatment of metals and plastics is therefore largely a service to many industries and examples of key customers are given below:

  • automotive
  • aerospace
  • information systems
  • telecommunications
  • heavy engineering
  • construction (building)
  • bathroom fittings
  • hardware
  • food and drink containers
  • printing
  • domestic appliances
  • jewellery, spectacles and ornaments
  • furniture
  • clothing
  • coinage
  • medical

The market structure in volume is approximately:

automotive 22 %
construction 9 %
food and drink containers 8 %
electric industry 7 %
steel semi product 7 %
electronic industry 7 %
industrial equipment 5 %
aerospace industry 5 %
unspecified 30 %

The following Table sets out examples of key treatments and their uses.

Examples of key treatments and their uses.jpg

1.2 Industry structure and economic background

1.2.1 Type and size of installations

The surface treatment of metals and plastics discussed in this document is carried out in more than 18300 installations (both IPPC and non-IPPC) in Europe, ranging from small private companies to facilities owned by multinational corporations. The large majority are small or medium enterprises (SMEs); in Germany the typical number of employees is between 10 and 80. Altogether, the industry for the surface treatment of metals and plastics employs about 440000 people in Europe. These figures include manufacturers of printed circuit boards. More than 10000 (55 %) are specialist surface treatment installations (known as job or jobbing shops). The remaining 8300 (45 %) are surface treatment shops within another installation typically also an SME. The majority of jobbing shops serve more than one industry (see those listed in Table 1). There is no installation typical of the whole range of activities, and even though there are strong similarities between sites engaged in the same activities, no two sites will be identical. For gathering economic statistics, electroplating, plating, polishing, anodising and colouring are classified under the Standard Industrial Classification (SIC) code 3471, but this includes establishments engaged in all types of metal finishing. Companies that both manufacture and finish (surface treat) products are classified according to the products they make. For data on sources of emissions, the industry is classed under general purpose manufacturing processes (for emissions, NOSE-P 105.01). These groupings make the extraction of data for specific surface treatments or for the whole sector difficult as they cannot be differentiated readily from the other engineering activities. Surface treatment is positioned between initial workpiece or substrate manufacture and final product assembly, completion and packaging. Treatment (both in jobbing shops and many inhouse workshops) often has low priority in the production chain, although there are significant exceptions. Low priority can result in insufficient attention to correct and up to date specifications, insufficient attention given in product design to minimise and reduce consumptions, as well as a lack of investment. Surface treatment is usually carried out after the primary metal or plastic has been formed into workpieces or shaped substrates, such as nuts, bolts, pressed or moulded components, sheets, or coils. They may even be sub-assemblies made of several components, often of different materials. These components and sub-assemblies can be complex shapes which have been pressed, cast and/or machined. However, in coil processing the surface treatment is applied before the substrate used. The size varies from wires to steel strip 2008 mm wide. In smaller scale reel-to-reel applications, copper, brass or other alloys are also coated. Printed circuit boards are made from plastic or glass fibre boards which are already laminated (usually with copper) or plastic films. Process lines are usually modular, and small lines can be easily assembled as a series of tanks. However, large automated lines and the modules in those installations handling steel coil on a large scale, or large components such as parts of aircraft wings, are typically specialist, large and capital intensive. Most installations, particularly the jobbing shops, will operate multiple lines side by side. This assists in increased capacity and reliability of delivery, and allows the installation to offer different treatments (jig, coil or small scale coil) for different products and prices and/or to offer different finishes.

As an example of geographic distribution and structure of the industry, in France the industry is widely spread, with concentrations in the south east (21 %) and the Paris area (24 %). The number of surface treatment installations where the volume of treatment vats exceed 1.5 m3 is 2250 (the threshold level for French national legislation), and the number where the volume of treatment vats exceed 10 m3 is 1260.

1.2.2 Equipment lifetime

The vast majority of process lines are modular and the actual plant life is difficult to quantify as individual modules are repaired or replaced as necessary. Typically, complete production lines are only replaced at long intervals (when maintenance of individual modules is no longer sufficient), or when radically new technology is introduced. However, for large scale surface treatment operations such as steel coil coating and treating automotive bodies and panels, capital investment can be many millions of euros (and up to EUR 500 million for a complete paint shop installation) with a lifetime of 20 to 40 years. Depreciation is usually over 20 years.

1.2.3 Technical characteristics of installations

Due to the modular nature of the process lines, some techniques can be installed or changed relatively quickly and cheaply. For instance, some process solutions are changed on a regular basis, others are expensive with a long life and change is an investment decision. Some techniques may require alterations or extensions to production lines. Although the modular nature facilitates such changes, in many cases other factors will affect the ease of change, such as the limits of transporter mechanisms and control systems, and the space available in the installation. In-house operations tend to be for specific products. Introducing changes for these and for plants handling larger products such as steel coil coating, aerospace parts or automotive bodies may be technically more difficult and/or involve higher capital costs. For larger plants, depreciation is usually between 6 and 20 years. Because of overcapacity in the sector, it is rare for totally new plants to be built. In existing installations, it is more common to replace modules or lines.

1.2.4 Market structure Competition
The low cost and ease of modular construction of lines is a low barrier to entry. Businesses treating the surfaces of metals and plastics using only one or two process lines, often of small vat volumes, are frequently in direct competition for some customers with installations operating larger process lines utilising more abatement techniques. While this industry serves several major manufacturing areas, there is a high concentration of customers in some areas (such as the automotive industry) with highly competitive markets, and surface treatment overcapacity. Very few jobbing shops are large enough to serve more than three or four industry types or provide more than three finish options, with most company business strategies focused on specialising in certain finish types. There are some limited opportunities to differentiate the business by providing specialist treatment finishes and/or by specialist quality standards, or for vertical integration such as manufacturing the components to be treated. The in-house installation is the complete vertical integration of the business. The large scale production lines depend on large volumes of very specific surface finishes, such as one type of coating for steel coil, and typically opportunities for diversification or new markets are extremely limited. Extent of the market
The geographic size of the market is often proportional to the degree of specialisation of the treatment. Those treatments that are widely carried out by jobbing shops (such as zinc plating with chromium passivation) are carried out on a very local basis, with customers usually controlling the price. Other, more specialised, finishes where the higher price justifies transport costs (such as cadmium plating or anodising of large components to aerospace specifications) may be carried out on a national scale, or even between neighbouring countries. However, the concentration of surface treatment installations within Europe usually means physically extending markets brings more competitors within range. The extent of the market for the customers’ goods is also an important factor. During 2001 and 2002 the volume of business in the light engineering industries fell by 30 % across Europe. This was due to the increased exporting of the total manufacture of engineered components and assemblies to Asia (Verbal discussions, TWG). Current predictions for printed circuit board (PCB) production are that by 2005/6 the worldwide PCB production may again reach the level of the boom year 2000. Due to the cost structure of Asian competitors, the long-term competitiveness of high volume PCB production in Europe using standard technologies remains questionable with global customers. Worldwide overcapacity may result in further mergers and insolvencies, unless further growth is generated in Europe. The percentage growth of multilayer boards (MLBs) and other high-tech products, including the disproportionate growth of HDI (high density interconnect) or microvia boards, demonstrates the technological development of European PCB production. It is expected that European PCB manufacturers will continue to move to high-tech areas, concentrating in segments such as sensor technology, industrial applications, telecommunications, automotive electronics, and medical and aeronautical industries. Market substitutes
Substitutes in this context means alternative, competing ways for the customer to achieve the desired result, and not the substitution for chemicals or other processes. Alternatives are readily available for many of the surface treatments of metals and plastics. The customer may change to one of these alternatives because of price or for design reasons. This type of substitution can take three forms:
  • a different surface treatment system. For example, electrolytic or chemical treatments compete with surface treatments by solvent-painting: painted car door handles have largely replaced chrome-plated ones; lithographic printing from aluminium plates can be replaced by laser or ink jet for small runs
  • component manufacture from a different material. The customer may redesign the products or components from alternative materials, reducing the need for surface treatment. For example, paint or foodstuffs can be sold in plastic containers instead of metal cans; lithographic plates can be produced with different substrates such as plastics
  • a combination of the above. Car light reflectors can now be moulded from plastic with vapour deposition of a metal, instead of copper/nickel/chrome plating of a steel pressing.

1.2.5 Summary of general economic situation

Opportunities to pass increased costs to customers are limited because of:

  • the large number of surface treatment installations competing for a decreasing number of customers
  • the decline of engineering businesses in Europe
  • the increasing substitution options (as described above).

1.3 Key environmental issues

1.3.1 Overall

The STM industry plays a major role in extending the life of metals, such as in automotive bodies and construction materials. It is also used in equipment that increases safety or reduces consumption of other raw materials (e.g. plating of aerospace and automotive braking and suspension systems, plating precision fuel injectors for automotive engines to reduce fuel consumption, etc.). The main environmental issues arising from the surface treatment of metals and plastics relate to energy and water consumption, the consumption of raw materials, emissions to surface and groundwater, solid and liquid wastes and the site condition on cessation of activities. Surface treatments have traditionally been associated with large water usage creating a wet working environment, although many installations have moved away from this way of working. The chemicals used have the potential to cause environmental harm particularly to surface waters, groundwaters and soil. Metals removed from waste waters end up in solid wastes and, together with some used process solutions, may need special management for recovery or disposal. The industry can discharge fumes and dust to air, as well as generating noise. The sector is a significant user of electricity, water and non-renewable resources (metals). The following issues are crucial:

  • minimisation of the consumption of raw materials, energy and water
  • minimisations of emissions by process management and pollution control
  • minimisation of waste production and its management
  • improvement of chemical safety and reduction of environmental accidents.

The measures to achieve better environmental performance are frequently complex and have to be assessed in respect to their potential impacts on the product and other processes (both preand post-treatment), the age and type of installation as well as the benefits to the environment as a whole. Best available techniques will be balanced against these criteria and therefore include changes within process units as well as end-of-pipe abatement techniques. Sophisticated process and treatment techniques play an important part in achieving improved environmental performance. Competent operation and regular maintenance are as essential as the choice of technology. Important considerations therefore include good management and working practices, good process and site design, education of the workforce on environmental and process performance, workplace safety and accident prevention, and finally, monitoring of the process and environmental performance.

1.3.2 Energy

Electricity is consumed in electrolytic and other electrochemical reactions (inter alia, electroplating and anodic oxidation). Electricity is also used to operate the process plant and equipment such as pumps, transporter equipment, other motors and compressors. It may also be used for supplementary vat heating (by immersion heaters) as well as space heating and lighting in the installation. There are transmission losses when electricity is transformed from high to low voltages. Energy can also be lost when drawing from more than one phase (reactive energy), as well as in DC (direct current) supplies to the treatment lines. Energy is lost, too, as heat when electric current is passed through the treatment solutions: some process chemistries are less energy efficient than others. Energy is also consumed in raising the temperature of the process baths, in drying components and for other heating activities. Losses occur from evaporation and as radiant heat from equipment. Some process chemistries require more heat energy than others. Energy is also used in drying workpieces or substrate and in extracting process fumes. Cooling can consume significant amounts of water in open flow or some cooling towers, and electricity is consumed by sealed refrigerating systems.

Literature: BAT for the Surface Treatment of Metals and Plastics, August 2006