Contents
vii
3.13.1 Preventive Measures ............................................................. 75
3.14 Filiform Corrosion .............................................................................. 75
3.14.1 Preventive Measures ............................................................. 76
References ....................................................................................................... 76
4 Atmospheric Corrosion ...............................................................................77
4.1 Atmospheric Types ............................................................................. 78
4.2 Factors Affecting Atmospheric Corrosion....................................... 79
4.2.1 Time of Wetness .....................................................................80
4.2.1.1 Adsorption Layers ..................................................80
4.2.1.2 Phase Layers ............................................................ 81
4.2.2 Composition of Surface Electrolyte .....................................83
4.2.2.1 Oxygen .....................................................................83
4.2.2.2 SO x ............................................................................83
4.2.2.3 NO x ...........................................................................83
4.2.2.4 Chlorides .................................................................84
4.2.2.5 CO 2 ............................................................................84
4.2.2.6 Concentration of Different Species ......................84
4.2.3 Temperature ............................................................................84
4.2.4 Initial Exposure ......................................................................85
4.2.5 Sheltering ................................................................................85
4.2.6 Wind Velocity ......................................................................... 86
4.2.7 Nature of Corrosion Products .............................................. 86
4.2.8 Pollutants Present .................................................................. 87
4.3 Mechanisms of Atmospheric Corrosion of Metals ........................ 89
4.3.1 Damp Atmospheric Corrosion (Adsorption Layers) ........90
4.3.2 Wet Atmospheric Corrosion (Phase Layers) ...................... 92
4.3.2.1 Dew .......................................................................... 92
4.3.2.2 Rain .......................................................................... 92
4.3.2.3 Fog ............................................................................ 93
4.3.3 Deposit of Pollutants ............................................................. 93
4.4 Corrosion Products ............................................................................. 94
4.5 Specific Atmospheric Corrodents ..................................................... 96
4.5.1 Sulfur-Containing Compounds ........................................... 97
4.5.2 Nitrogen-Containing Compounds ...................................... 99
4.5.3 Chlorine-Containing Compounds .................................... 100
4.5.4 Carbon Dioxide (CO 2 ) .......................................................... 101
4.5.5 Oxygen (O 2 ) ........................................................................... 101
4.5.6 Indoor Atmospheric Compounds ..................................... 101
4.6 Summary ............................................................................................ 101
4.7 Resistance of Specific Metals and Alloys to Atmospheric
Corrosion ............................................................................................ 102
4.7.1 Carbon Steel .......................................................................... 102
4.7.2 Weathering Steels................................................................. 104
4.7.3 Zinc ........................................................................................ 106
vii
3.13.1 Preventive Measures ............................................................. 75
3.14 Filiform Corrosion .............................................................................. 75
3.14.1 Preventive Measures ............................................................. 76
References ....................................................................................................... 76
4 Atmospheric Corrosion ...............................................................................77
4.1 Atmospheric Types ............................................................................. 78
4.2 Factors Affecting Atmospheric Corrosion....................................... 79
4.2.1 Time of Wetness .....................................................................80
4.2.1.1 Adsorption Layers ..................................................80
4.2.1.2 Phase Layers ............................................................ 81
4.2.2 Composition of Surface Electrolyte .....................................83
4.2.2.1 Oxygen .....................................................................83
4.2.2.2 SO x ............................................................................83
4.2.2.3 NO x ...........................................................................83
4.2.2.4 Chlorides .................................................................84
4.2.2.5 CO 2 ............................................................................84
4.2.2.6 Concentration of Different Species ......................84
4.2.3 Temperature ............................................................................84
4.2.4 Initial Exposure ......................................................................85
4.2.5 Sheltering ................................................................................85
4.2.6 Wind Velocity ......................................................................... 86
4.2.7 Nature of Corrosion Products .............................................. 86
4.2.8 Pollutants Present .................................................................. 87
4.3 Mechanisms of Atmospheric Corrosion of Metals ........................ 89
4.3.1 Damp Atmospheric Corrosion (Adsorption Layers) ........90
4.3.2 Wet Atmospheric Corrosion (Phase Layers) ...................... 92
4.3.2.1 Dew .......................................................................... 92
4.3.2.2 Rain .......................................................................... 92
4.3.2.3 Fog ............................................................................ 93
4.3.3 Deposit of Pollutants ............................................................. 93
4.4 Corrosion Products ............................................................................. 94
4.5 Specific Atmospheric Corrodents ..................................................... 96
4.5.1 Sulfur-Containing Compounds ........................................... 97
4.5.2 Nitrogen-Containing Compounds ...................................... 99
4.5.3 Chlorine-Containing Compounds .................................... 100
4.5.4 Carbon Dioxide (CO 2 ) .......................................................... 101
4.5.5 Oxygen (O 2 ) ........................................................................... 101
4.5.6 Indoor Atmospheric Compounds ..................................... 101
4.6 Summary ............................................................................................ 101
4.7 Resistance of Specific Metals and Alloys to Atmospheric
Corrosion ............................................................................................ 102
4.7.1 Carbon Steel .......................................................................... 102
4.7.2 Weathering Steels................................................................. 104
4.7.3 Zinc ........................................................................................ 106