© 2006 by Taylor & Francis Group, LLC

More documents

Recommendations

Info

110 Corrosion Control Through Organic Coatings and, being upwind, does not suffer from the refinery. However, they also noted heavy amounts of dust on the samples at this site, almost certainly from the cement factory next door. Analysis of the dust showed it to be similar to the composition of clinker cement. Cement, of course, is extremely alkaline, to which few polymers are resistant. At the high temperatures at these sites — up to 49°C — and with the very high amounts of water vapor available, soluble alkaline species in the dust deposits can form a destructive, highly alkaline solution that can break down cured binder. The extent to which the various coatings managed to retain gloss at this site is almost certainly a reflection of the polymer’s ability to resist saponification. In a study of coated panels exposed throughout two pulp and paper mills in Sweden, Rendahl and colleagues [37] found that the amounts of airborne H 2S and SO 2 at the various locations did not have a significant impact on coating performance. The effect of airborne chlorine in this study is not clear; the authors note that only total chlorine was measured, and the amounts of active corrosion-initiating species at each location are unknown. Özcan and colleagues [38] examined the effects of very high SO 2 concentrations on polyester coatings. Using 0.286 atmosphere SO 2 (to simulate conditions in flue gases) and humidity ranging from 60% to 100% RH, they found that corrosion occurred only in the presence of water. At 60% RH, no significant corrosion damage occurred, despite the very high concentration of SO 2 in the atmosphere. Another study, performed in Spain, indicates that humidity played a more important role than levels of atmospheric contaminants in predicting corrosion of painted steel [39]. However, without quantitative data of pollutant levels for Madrid and Hospitalet, it is impossible to rule out a combination of humidity and airborne pollutants as the major factor in determining coating performance. In this study, 60 µm chlorinated rubber was applied to clean steel. Painted samples and coupons of bare steel and zinc were exposed in dry rural, dry urban, humid industrial, and humid coastal areas. The results after two years are given in Table 6.3. TABLE 6.3 Performance of Bare Steel and Coated Panels Location Type of atmosphere Humid/Dry Corrosion of bare steel (lm/year) Degree of oxidation of painted surface (%) after 2 years El Pardo Rural Dry 14.7 0 Madrid Urban Dry 27.9 0 Hospitalet Industrial Humid 52.7 0.3 Vigo Coastal Humid 62.6 16 Modified from: Morcillo, M. and S. Feliu, Proc., Corrosio i Medi Ambient, Universitat de Barcelona, Barcelona, 1986, 312. © 2006 by Taylor & Francis Group, LLC
Weathering and Aging of Paint 111 In a 1950s British study of bare steel and painted panels carried out at Sheffield, an industrial site that had heavy atmospheric pollution at the time, and Calshot, a marine site, the same overall result — no correlation between airborne chemicals and corrosion of painted metal — was seen [40]. The corrosion rate of bare steel in Sheffield was about four times that at Calshot, but the performance of the painted panels was about the same (see Table 6.4). The same trend was seen in a Portuguese study of zinc-rich coatings exposed at Sines (marine atmosphere) and Lavradio (industrial). Bare metal coupons of mild steel corroded nearly twice as much at Lavradio as at Sines, and zinc corroded almost four times as much at Lavradio. The 18 coatings studied at both sites did not reflect that difference [41]. REFERENCES TABLE 6.4 Comparison of Bare Steel and Painted Panels at Sheffield and Calshot Sheffield Calshot Type of environment Industrial Marine Rate of corrosion of mild steel over 5 years, µm/year 109 28 Life to failure of a 4-coat painting scheme, years 6.1 6.0 Modified from: Sixth Report of the Corrosion Committee, Special Report No. 66, Iron and Steel Institute, London, 1959. 1. Ranby, B. and Rabek, J.F., Photodegradation, Photo-oxidation and Photostabilization of Polymers: Principles and Application, Wiley Interscience, New York, 1975, 242. 2. Forsgren, A. and Appelgren, C., Performance of Organic Coatings at Various Field Stations After 5 Years’ Exposure, Report 2001:5E, Swedish Corrosion Institute, Stockholm, 2001. 3. Krejcar, E. and Kolar, O., Prog. Org. Coat., 3, 249, 1973. 4. Hare, C.H., J. Prot. Coat. Linings, 17, 73, 2000. 5. Berg, C.J., Jarosz, W.R. and Salanthe, G.F., J. Paint Technol., 39, 436, 1967. 6. Nichols, M.E. and Darr, C.A., J. Coat. Technol., 70, 885, 1998. 7. Oosterbroek, M.L. et al., J. Coat. Technol., 63, 55, 1991. 8. Miller, C.D., J. Amer. Oil Chem. Soc., 36, 596, 1959. 9. Marshall, N.J., Off. Dig., 29, 792, 1957. 10. Fitzgerald, E.B., in ASTM Bulletin 207 TP-137, American Society for Testing and Materials, Philadelphia, PA, 1955, 650. 11. Hare, C.H., J. Prot. Coat. Linings, 13, 65, 1996. 12. Allen, N.S. et al., Prog. Org. Coat., 32, 9, 1997. © 2006 by Taylor & Francis Group, LLC
Page 1 and 2:
© 2006 by Taylor & Francis Group,
Page 3 and 4:
Corrosion of Ceramic and Composite
Page 5 and 6:
Published in 2006 by CRC Press Tayl
Page 7 and 8:
Preface This book has been written
Page 9 and 10:
Author Amy Forsgren received her ch
Page 11 and 12:
Contents Chapter 1 Introduction ...
Page 13 and 14:
2.4.2 Reactive Reagents ...........
Page 15 and 16:
6.2.4.1 Alkaline Blistering........
Page 17 and 18:
1 Introduction This book is not abo
Page 19 and 20:
Introduction 3 • A dissolution pr
Page 21 and 22:
Introduction 5 1.2.2 ELECTROLYTIC R
Page 23 and 24:
Introduction 7 to the metal is a ne
Page 25 and 26:
Introduction 9 9. Thomas. N.L., Pro
Page 27 and 28:
12 Corrosion Control Through Organi
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74: 58 Corrosion Control Through Organi
Page 81 and 82: 4 Blast Cleaning and Other Heavy Su
Page 83 and 84: Blast Cleaning and Other Heavy Surf
Page 99 and 100: 5 Abrasive Blasting and Heavy-Metal
Page 101 and 102: Abrasive Blasting and Heavy-Metal C
Page 113 and 114: 6 Weathering and Aging of Paint Thi
Page 115 and 116: Weathering and Aging of Paint 101 c
Page 117 and 118: Weathering and Aging of Paint 103 I
Page 119 and 120: Weathering and Aging of Paint 105 c
Page 121 and 122: Weathering and Aging of Paint 107 S
Page 123: Weathering and Aging of Paint 109 e
Page 127 and 128: 7 Corrosion Testing — Background
Page 129 and 130: Corrosion Testing — Background an
Page 143 and 144: 130 Corrosion Control Through Organ
Page 167: 154 Corrosion Control Through Organ
show all

© 2006 by Taylor & Francis Group, LLC

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?