the atmosphere,a mmonium nitrite andn itrate arep roduced. Both
compounds increase the rate of zinc corrosion, but less than SO 2 or SO 3 .
Because of the Mears effect (wire corrodes faster per unit of area than more
massive materials) galvanized wire corrodes some 10–80% faster than
galvanized sheet. However,the life of rope made from galvanized steel wires
is greater than the life of the individual wire. This is explained by the fact
that the parts of the wire that lie on the outside are corroded more rapidly
and when the zinc film is penetrated in those regions, the uncorroded zinc
inside the rope provides cathodic protection for the outer regions.
Table 7.10 lists the compatibility of zinc coatings with variouscorrodents.
TABLE 7.10
Compatibility of Galvanized Steel with Selected
Corrodents
AceticAcid
U
Acetone
G
Acetonitrile
G
Acrylonitrile
G
Acrylic latex
U
Aluminum chloride, 26%
U
Aluminum hydroxide
U
Aluminum nitrate
U
Ammonia, dry vapor
U
Ammoniuma cetate solution
U
Ammoniumb isulfate
U
Ammoniumb romide
U
Ammoniumc arbonate
U
Ammoniumc hloride, 10%
U
Ammoniumd ichloride
U
Ammoniumh ydroxide
Vapor
U
Reagent
U
Ammoniumm olybdate
G
Ammoniumn itrate
U
Argon
G
Barium hydroxide
Barium nitratesolution
S
Barium sulfatesolution
S
Beeswax
U
Borax
S
Bromine, moist
U
2-Butanol
G
Butyl acetate
G
Butyl chloride
G
Butyl ether
G
Butylphenol
G
Cadmium chloride solution
U
Cadmium nitrate solution
U
Cadmium sulfate solution
U
Calcium hydroxide
Sat. solution
U
20% Solution
S
Calcium sulfate,sat. solutionU
(continued)
Coatings
445
CAT8247—CHAPTER 7—17/10/2006—15:03—TRGANESH—XMLM ODEL B–pp. 403–485