Page 261 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

CORROSION CONTROL OF BRIDGES 239

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The costs of total paint removal and repainting can range from $43/m to
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$215.25/m , which may be explained by the fact that each job is unique in the
sense of access for high structures or structures over water, the condition of bridge
deterioration, and unusual traffic control.
An alternative to paint removal is overcoating that includes cleaning the structure,
priming rusty portions, and applying intermediate coats and topcoats either on the
repaired areas or over the full structure. The cost of overcoating bridges can range
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from $11 to $54/m and the tighter standards may raise the cost to $86/m .
The effort to implement bridge corrosion control maintenance practices, which
achieve regulatory requirements and cost efficiency, cannot be successful without the
development of reliable task-based cost data for bridge painting tasks. These data
depend on many factors such as local labor costs and structural factors such as acces-
sibility to contractor costing rules.
It is estimated that nearly 50% of the cost of an average painting job is attributed to
environmental protection and workers’ health measures. This resulted in the increase
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in the cost of the coating removal job from $54.36/m in 1992 to $114.10/m in 1995.
It is to be noted that the cost of the actual work such as surface preparation and coating
materials remained relatively constant.
The estimated time to failure for several coating systems is given in Table 4.19.
Table 4.20 gives the estimated costs for painting options (34, 35).
In Table 4.19, lifetime is defined as 10% degradation of the coatings. The data
presented show that depending on the type of surface preparation (blasting versus
surface coating) and the type of coating, the service life can vary considerably from
3 to 30 years. Similarly, Table 4.20 suggests that the longevity of coating is related
to the costs of surface preparation and coating application. For example, overcoating
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costs $3.22/m and lasts only a few years while near-white metal blasting followed
by metallizing costs 10 times more and lasts for 30 years.
The data given in Table 4.20 also contains extra costs such as containment and
waste-disposal-related costs and worker health and safety costs. The numbers show
that these types of costs are equal to or exceed the costs of surface preparation, coating
material, and coating application.
A sample cost distribution shown in Table 4.21 for a typical heavy-duty mainte-
nance job on a steel bridge structure shows that only a small portion of the total job
cost is attributed to paint and its application (34).

TABLE 4.19 Coating System Time-to-Failure Estimates in Marine Environment
Coating System Estimated Life

Ethyl silicate inorganic zinc/epoxy polyamide Aliphatic urethane over 15 years
SP-10 near-white metal blast
Epoxy mastic/aliphatic urethane over Sp-10 near-white metal blast 10 years
Epoxymastic/aliphatic urethane overcoat over existing paint and SP-3 4 years
85% zinc and 15% aluminum metallizing over SP-10, near-white metal 30 years
blast
Low-VOC alkyd three-coat system overcoat over existing paint and SP-3 3 years