Page 294 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

272 CORROSION CONTROL AND PREVENTION

TABLE 4.33 Types and Frequency of Failure of Copper Plumbing in the United States
in 1983
Cause of Failure Frequency (%)
Pitting corrosion 58
Erosion-corrosion 24
Corrosion of outer surface of tubes 7
Faulty workmanship 5
Fatigue 2
Other 4
Total 100

result in lead levels greater than an EPA level of 15 ppb. Cold water lines generally
have less lead than hot water lines. Orthophosphate may be used to control the release
of lead in water (51). When the lead content of the water is too high, the alternate
control method is to replace the home plumbing with new (copper) pipes.
Copper has been the most common material for consumer plumbing because
of its excellent characteristics such as ease of installation, low cost, and corrosion
resistance. Cooper accounts for 50–90% of all tubes installed in drinking water
services (52). Corrosion problems, although infrequent, can be severe for the affected
consumers and systems. Failure of copper tubing by pitting, blue or green water
problems, and failure to meet the US EPA levels for copper in tap water are major
problems when they occur. The different causes of copper tubing failure are noted in
Table 4.33 (45).
Corrosion control methods for copper corrosion are: (i) improved production tech-
niques that yield a clean inner bore and free from carbon films, which initiate pitting.
The main practice is to use iron grit for blasting to remove carbon films; this process
reduces the frequency of pitting by 90%. Another technique is to preoxidize the inner
bore that removes the carbon film and produces an oxide film that improves the resis-
tance to corrosion. Chemical treatment of the water supply is also a method used to
reduce the corrosive attack on copper pipes.
Nonferrous alloys are used in domestic plumbing systems such as fixtures, fit-
tings, or joints. These alloys act as a source of lead contamination in drinking water.
Other elements of concern are copper, tin, zinc, antimony, and bismuth. The cor-
rosion mechanisms vary greatly for each different alloy system, and the local water
composition has profound influence on the corrosion susceptibility of different alloys.
Corrosion control methods for nonferrous alloys include preventive measures such as
replacement of fixtures or a complete change of material design. Corrosion of non-
ferrous alloys is minimized by using industry-standard materials and workmanship
in the installation of copper tubing systems.

4.18.6.2 Requirements to Conduct Corrosion Control Chemical analysis of the
water and adoption of a corrosion control strategy to reduce the lead release rates
are required. Drinking water is analyzed for corrosion by: (i) weight loss, (ii) total