Reference Document on Best Available Techniques for the

6,01
MB Surface Treatment of Metals and Plastics

582
stron

6070
ID JRC-IPTS Instituto de Prospectiva Tecnológica (IPTS)

2006
rok

EXECUTIVE SUMMARYI

PREFACEXI

SCOPE XXXIII

1 GENERAL INFORMATION ON THE SURFACE TREATMENT OF METALS AND PLASTICS. 1

1.1 Industries using surface treatments 2

1.2 Industry structure and economic background. 4

1.2.1 Type and size of installations. 4

1.2.2 Equipment lifetime. 5

1.2.3 Technical characteristics of installations 5

1.2.4 Market structure . 5

1.2.4.1 Competition 5

1.2.4.2 Extent of the market . 6

1.2.4.3 Market substitutes 6

1.2.5 Summary of general economic situation 7

1.3 Specific industry activities . 7

1.3.1 Anodising of aluminium architectural panels and profiles. 7

1.3.2 Large scale continuous coating of steel 9

1.3.3 Coil and sheet anodising for lithographic (offset) printing plates 12

1.3.4 Continuous coil processing of aluminium 12

1.3.5 Printed circuit boards . 12

1.4 Key environmental issues. 14

1.4.1 Overall . 14

1.4.2 Water. 14

1.4.3 Energy. 15

1.4.4 Substances of concern 16

1.4.4.1 Metals. 18

1.4.4.2 Cyanides. 19

1.4.4.3 Hypochlorite, chlorine and AOX . 19

1.4.4.4 Surfactants 19

1.4.4.5 Complexing agents. 19

1.4.4.6 Acids and alkalis 19

1.4.4.7 Other ions. 20

1.4.4.8 Solvents 20

1.4.4.9 Dusts 20

1.4.4.10 Wastes 20

1.4.5 Other emissions 20

1.4.5.1 Noise 20

1.4.5.2 Odour . 21

2 APPLIED PROCESSES AND TECHNIQUES 23

2.1 Delivery and storage – workpieces and consumable raw materials . 27

2.1.1 Incoming workpiece and/or substrates to be treated 27

2.1.2 Consumable raw materials . 28

2.2 Handling techniques for processing and loading for processing 29

2.3 Workpiece or substrate pretreatment 31

2.3.1 Mechanical pretreatment 31

2.3.1.1 Linishing and polishing 31

2.3.1.2 Abrasive blasting 32

2.3.1.3 Deburring and/or tumbling. 32

2.3.2 Electrolytic and chemical polishing . 32

2.3.2.1 Electropolishing . 33

2.3.2.2 Electropolishing with electric discharge (also known as plasma-electrolytic polishing) . 33

2.3.2.3 Electrolytic and chemical polishing processes for aluminium. 34

2.3.3 Solvent degreasing . 34

xvi Surface Treatment of Metals and Plastics

2.3.4 Aqueous cleaning .35

2.3.5 Other cleaning techniques 36

2.3.5.1 Air knives .36

2.3.5.2 Centrifuges36

2.3.5.3 Dry ice 36

2.3.5.4 Hand wiping .36

2.3.6 Pickling, descaling and desmutting 37

2.3.7 Etching and descaling of aluminium 38

2.3.8 Electrolytically assisted pickling, activation and degreasing38

2.3.9 Metal stripping39

2.3.10 Pretreatment of plastics (etching) .39

2.3.10.1 Conditioning of plastics39

2.3.10.2 Etching or pickling of plastic40

2.4 Drag-out and rinsing .40

2.5 Core activities .41

2.5.1 Copper and copper alloy plating.41

2.5.1.1 Cyanide copper .42

2.5.1.2 Acid copper.42

2.5.1.3 Pyrophosphate copper.43

2.5.1.4 Brass .43

2.5.1.5 Bronze.43

2.5.2 Nickel electroplating.44

2.5.2.1 Watts-type nickel solutions.45

2.5.2.2 Nickel sulphamate-based solutions.46

2.5.2.3 Nickel chloride-based solutions47

2.5.2.4 Nickel sulphate-based solutions47

2.5.2.5 Other nickel plating solutions .47

2.5.2.6 Nickel alloy plating solutions .47

2.5.3 Chromium plating.48

2.5.3.1 Bright chromium plating (hexavalent chromium electrolytes) .49

2.5.3.2 Bright chromium plating (trivalent chromium electrolytes) .49

2.5.3.3 Black chromium plating .49

2.5.3.4 Hard chromium plating.50

2.5.4 Zinc and zinc alloy plating .50

2.5.4.1 Alkaline cyanide zinc .51

2.5.4.2 Alkaline cyanide-free zinc 51

2.5.4.3 Acid zinc.52

2.5.4.4 Zinc alloy plating52

2.5.5 Cadmium plating 53

2.5.6 Tin and alloy plating.54

2.5.7 Precious metal plating 54

2.5.7.1 Silver.55

2.5.7.2 Gold 55

2.5.7.3 Palladium and alloys.56

2.5.7.4 Rhodium .56

2.5.7.5 Platinum57

2.5.8 Autocatalytic plating (catalytic chemically reduced coatings) .57

2.5.8.1 Autocatalytic nickel on metals58

2.5.8.2 Autocatalytic nickel coating for plastics.59

2.5.8.3 Autocatalytic copper on metals and plastics .59

2.5.9 Immersion or displacement coatings – non-catalytic chemically reduced coatings .60

2.5.10 Electropainting or electrocoating61

2.5.11 Lacquering.62

2.5.12 Oiling.62

2.5.13 Anodising .62

2.5.13.1 Sulphuric acid anodising of aluminium64

2.5.13.2 Chromic acid anodising of aluminium65

2.5.13.3 Anodising of magnesium, titanium, tantalum and niobium66

2.5.13.4 Phosphoric acid anodising 66

2.5.14 Colour anodising on aluminium .66

2.5.14.1 Immersion colouring.67

2.5.14.2 Electrolytic colouring .67

2.5.14.3 Interference colouring.67

2.5.14.4 Integral colouring . 67

2.5.15 Sealing following anodising. 67

2.5.15.1 Hot sealing . 68

2.5.15.2 Cold sealing 68

2.5.16 Phosphating layer conversion coatings 68

2.5.16.1 Alkali phosphating . 69

2.5.16.2 Zinc phosphating 70

2.5.16.3 Manganese phosphating . 71

2.5.17 Chromium conversion coatings 71

2.5.17.1 Chromium (VI) conversion coatings 72

2.5.17.2 Chromium (VI) conversion coatings on electroplated zinc layers . 72

2.5.17.3 Chromium (VI) conversion coatings on copper, brass and bronze. 72

2.5.17.4 Chromium (VI) conversion coatings on aluminium. 72

2.5.17.5 Chromium (VI) conversion coatings on magnesium and its alloys 73

2.5.17.6 Trivalent chromium (Cr(III)) conversion coatings on aluminium and electroplated zinc. 73

2.5.17.7 Topcoatings for chromate conversion coatings 74

2.5.18 Metal colouring 74

2.5.19 Bright dipping 75

2.5.20 Chemical blacking – oxide coatings. 75

2.5.21 Brightening 76

2.5.22 Etching – Alkaline etching of aluminium 76

2.5.23 Chemical milling 77

2.6 After treatment activities 78

2.6.1 Drying using hot water. 78

2.6.2 Drying using hot air . 78

2.6.3 Drying using air knives 78

2.6.4 Heat treatment for hydrogen de-embrittlement 79

2.7 Common techniques for water and waste water treatment, process solution maintenance and

materials recovery 79