Page 234 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

212 CORROSION CONTROL AND PREVENTION

Coating material
Waste disposal 4%
5%

Environment Access Costs
monitoring 9% 28%

Surface
preparation
10%

Coating
application
10%
Containment
19%

Worker health
15%
Figure 4.2 Cost distribution of coating application on steel highway bridge structure (7).

use lead-free paint. Currently, 4% of all coating sales is for the purpose of replacing
lead-based coatings. A third major change is the toxicity of chromates and its presence
in corrosion-inhibiting primers that are used in protecting aluminum alloys. Chro-
mates may be replaced with molybdates or tungstates in combination with sodium
nitrite.

4.2.2 Metallic Coatings
The most widely used metallic coating process for corrosion protection is galvaniz-
ing, which involves application of metallic zinc to carbon steel for corrosion protec-
tion purposes. The statistics of the Department of Commerce in 1998 state that nearly
8.6 million metric tons of hot-dip galvanized steel were produced in 1997 (8). The
total market for metallizing and galvanizing in the United States, which is considered
a corrosion control cost, is estimated at $1.4 billion. This figure represents the total
material cost of the metal coating and the cost of processing. This does not include
the cost of carbon steel that is being galvanized.

4.2.2.1 Galvanizing Hot-dip galvanizing differs from other zinc coatings and the
metallizing process in that the zinc is alloyed to the metal during galvanizing. In con-
trast, organic or inorganic zinc coatings including electroplated metallic coatings are