286
Fundamentals of Corrosion
the environment, which increases the relative performance factor compared
with galvanized steel.
8.4.1.4 Zinc-55% Aluminum Hot Dip Coatings
These coatings are known as Galvalume and consist of zinc-55% aluminum-1.5% silicon. This alloy is sold under tradenames as Zaluite, Aluzene,
Algalva, Algafort, Aluzinc, and Zincalume. Galvalume exhibits superior
96
84
72
60
48
Exposure Time (months)
= Galvanized × = Galfan
×
×
×
×
36
24
12
0
5
1–Side Thickness Loss (mm)
10
15
20
FigurE 8.14
Seven-year exposure of Galfan and galvanized steel in a severe marine atmosphere.
TabLE 8.6
Five-Year Outdoor Exposure Results of Galfan Coating
Atmosphere
Thickness Loss (µm)
Ratio of
Improvement
Galvanized
Galfan
Industrial
15.0
5.2
2.9
Severe marine
>20.0
9.5
>2.1
Marine
12.5
7.5
1.7
Rural
10.5
3.0
3.5
Structure of the corrosion cell.