environments. After approximately threey ears, the corrosion-time curves
take on am ore gradual slope reflecting ac hange from active,z inclike
behavior to passive, aluminumlike behavior as the interdentric regions fill
with corrosion products. It has been predicted that Galvalume sheets should
outlast galvanized sheets of equivalent thickness by at least two to four
timeso ver aw ide range of environments. Figures comparingt he corrosion
performance of galvanized sheeta nd Galvalumes heet ares hown in
Figure 7.17.
Galvalume sheets provide excellent cut-edge protection in very aggressive
conditions where the surfacedoes not remain too passive. However, it does
not offer as good aprotection on the thickersheets in mild rural conditions
Corrosion loss,
micrometers
15
10
5
0 02468
Exposure time,years
Industrial atmosphere
10 12 14 16
Galvanized
Galvalume
15
10
5
0 02468
Exposure time,years
Corrosion loss,
micrometers
Corrosion loss,
micrometers
Marine atmosphere
10 12 14 16
15
10
5
0 02468
Exposure time,years
Severe marine atmosphere
10 12 14 16
Galvanized
Galvanized
Galvalume
Galvalume
FIGURE 7.17
Thirteen year exposureo fGalvalume in marine and industrial atmospheres.
Corrosion of Linings and Coatings
450
CAT8247—CHAPTER 7—17/10/2006—15:03—TRGANESH—XMLM ODEL B–pp. 403–485