A Hot Box–Cold Box Investigation of the Corrosion Behavior of Highly Insulated Zinc Roofing Systems

Abstract

This paper investigates the effect of roofing systems on the humidityinduced corrosion of zinc sheeting in highly insulated zinc roofs. Ten types of roofing systems (U< 0.25 W/(m²K)) were tested in a hot box–cold box apparatus. The measurements and investigations include the relative humidity under the zinc sheeting, the corrosion type, the corrosion product, and the corrosion rate. The influence of a well performing air-vapor retarder below the insulation on the underside corrosion of zinc sheeting is slight for zinc roofs with a good cavity ventilation, but significant if the ventilation is poor. For nonventilated zinc roofs, installing a perfect air-vapor retarder under the insulation only is not sufficient to control the sheeting underside corrosion. Further introducing a dry capillary and sorption active material between the sheeting and the insulation greatly reduces that corrosion.

Keywords

metallic roofs corrosion roofing system condensation

Get full access to this article

View all access options for this article.

References

1. Anderson, E.A. (1955). The Atmospheric Corrosion of Rolled Zinc , In: ASTM STP 175, pp. 126–134 .

2. Larrabee, C.P. and Ellis, O.B. (1959). Corrosiveness of Various Atmospheric Test Sites as Measured by Specimens of Steel and Zinc , In: Proc. ASTM 59, pp. 183–201 .

3. Dunbar, S.R. (1968). The Effect of 1% Copper Addition on the Atmospheric Corrosion of Rolled Zinc , In: ASTM STP 435, pp. 308–325 .

4. Showak, W. and Dunbar, S.R. (1982). Effect of One Percent Copper Addition on Atmospheric Corrosion of Rolled Zinc After 20 Year’s Exposure , In: Atmospheric Corrosion of Metals, ASTM STP 767, pp. 135–162 .

5. Vilche, J.R. , Varela, F.E. , Acuna, G. , Codero, E.N. , Rosales, B.M. , Fernandez, A. and Moriena, G. (1995). A Survey of Argentinean Atmospheric Corrosion: I–Aluminium and Zinc Samples , Corrosion Science, 37(6): 941–961 .

6. Suzuki, I. (1989). Corrosion-Resistant Coating Technology, Corrosion Technology Series, In: Schweitzer, P.A. (ed.), Marcel Dekker, New York .

7. Sereda, P.J. (1974). Weather Factors Affecting Corrosion of Metals , In: Corrosion in Natural Environment, ASTM STP 558, pp. 7–12 .

8. Zahner, L.W. (1995). Architectural Metals: A Guide to Selection, Specification, and Performance, John Wiley & Sons, New York .

9. Odnevall, I. , Verbiest, P. , He, W. and Leygraf, C. (1998). The Influence of Patina Age and Pollution Levels on the Runoff Rate of Zinc from Zinc Materials , Corrosion Science, 40(11): 1977–1982 .

10.

10. Odnevall, I. , Verbiest, P. , He, W. and Leygraf, C. (2000). Effects of Exposure Direction and Inclination on the Runoff of Zinc and Copper Roofs , Corrosion Science, 42(9): 1471–1487 .

11.

11. Pohl, W.H. and Behr, R. (1999). Corrosion of Titanium Zinc Under Atmospheric Conditions , Metall. Jahrgang, 9(5): 254–259 , (in German).

12.

12. He, W. , Odnevall, I. and Leygraf, C. (2001). A Laboratory Study of Copper and Zinc Runoff During First Flush and Steady-state Conditions , Corrosion Science, 43(1): 127–146 .

13.

13. Dunbar, S.R. and Showak, W. (1982). Atmospheric Corrosion of Zinc and its Alloys, In: Ailor, W.H. (ed.), Atmospheric Corrosion, pp. 529–552, John Wiley & Sons, New York .

14.

14. Union Minie` re France (1996). Roofing Manual, VM ZINC.

15.

15. Janssens, A. , Depraetere, W. , Roels, S. , Morel, A.M. and Hens, H. (1997). VLIET PROEFGEBOUW, ZINKEN DAKEN, EERSTE JAARRAPPORT, (VLIET Test Building, Zinc Roofs, the First Year Report), Laboratorium Bouwfysica, K. U. Leuven, Belgium , (in Dutch).

16.

16. Zheng, R. , Janssens, A. , Carmeliet, J. , Bogaerts, W. and Hens, H. (2004a). An Evaluation of Highly Insulated Cold Zinc Roofs in a Moderate Humid Region – Part I: Hygrothermal Performance , Construction and Building Materials, 18(1): 49–59 .

17.

17. Zheng, R. , Janssens, A. , Carmeliet, J. , Bogaerts, W. , and Hens, H. (2004b). An Evaluation of Highly Insulated Cold Zinc Roofs in a Moderate Humid Region – Part II: Corrosion Behavior of Zinc Sheeting , Construction and Building Materials, 18(1): 61–71 .

18.

18. Hens, H. (1992). Luft-Winddichtigkeit von geneigten Dachern. Wie sie sich wirklich verhalten, (Air-wind-tightness of Pitched Roofs – Their Real Behavior, in German) Bauphysik, 14(H.6): 161–174 .

19.

19. Friel, J.J. (1986). Atmospheric Corrosion Products on Al, Zn, and AlZn Metallic Coatings , Corrosion, 42: 422–426 .

20.

20. Odnevall, I. and Leygraf, C. (1994a). The Formation of Zn4SO4(OH)64H2O in a Rural Atmosphere , Corrosion Science, 36(6): 1077–1091 .

21.

21. Odnevall, I. and Leygraf, C. (1994b). The Formation of Zn4CI2(OH)4SO45H2O in an Urban and an Industrial Atmosphere , Corrosion Science, 36(9): 1511–1567 .

22.

22. ASTM Designation (1994). G 46-94: Standard Guide for Examination and Evaluation of Pitting Corrosion, Annual Book of ASTM Standards, Volume 03.02, Wear and Erosion; Metal Corrosion .

23.

23. Aziz, P.M. (1956). Application of the Statistical Theory of Extreme Values to the Analysis of Maximum Pit Depth Data for Aluminum , Corrosion, 12: 495–506 .

24.

24. Zheng, R. (1999). Investigations in the Corrosion of Zinc Sheeting of Highly Insulated Zinc Roofs in the VLIET Test Building, Internal Report, Laboratory of Building of Physics, KU Leuven, Belgium .

25.

25. Building Research Establishment (January 1986). Zinc-coated Steel, Building Research Establishment Digest, Digst 305, UK.

26.

26. Gilbert, P.T. and Hadden, S.E. (1950). “White rust” Formation on Zinc , J. Inst. Metals, 78: 47–70 .