Copper Alliance HSDG Australia

Limitations of Copper Tubes – Corrosion
Balanced water chemistry is important to the corrosion resistance of copper piping.
History Of Copper Plumbing Systems
Copper tube is recognised as a reliable
material for plumbing water supply and
sanitary systems due to its successful &
widespread international usage. Copper has
been used in plumbing systems worldwide
for over 100 years. There have been a small
number of cases where copper plumbing
has suffered premature failure from pitting or
discolouration of water due to the presence
of copper species from corrosion or effects
from the external environment.
Research undertaken over recent years
has demonstrated that water chemistry
is the primary factor influencing these
failure processes. The other significant
contributing factor is design and installation
issues such as pipe sizing, flow rates or
contact with incompatible materials such as
aggressive soils.
Balanced water chemistry is important to
the corrosion resistance of copper piping.
Transient conditions may either prevent the
formation of uniform, protective, internal
films, or cause irreparable damage.
Copper water piping achieves its longevity
through the development of a stable
protective internal surface film. Corrosion
may occur if either an unstable film forms, or
a protective film is interfered with during the
installed life of the water pipe.
Types of Copper Corrosion
Microbiologically Influenced Corrosion
(MIC)
The MIC mechanism involves the presence
of a biofilm which has the capability of
adhering itself to a metal surface.
When biological material lodges on the metal
surface, it forms concentration cells due
to the development of micro colonies of
bacteria (Figure 6.1). A pH gradient is
established within the region, with a lower pH
produced at the film layer close to the metal,
which corrodes.
It is important to note that:
• The formation of biofilms is related to
water chemistry not the metal.
• International investigations have shown
copper to have superior resistance to
the impact of bacteria compared to
alternative piping materials.
MIC generally affects only cold water (Figure
6.1), and is more likely in untreated water
supplies. Hot water systems where the water
is maintained above 60 0 C and treated water
where a disinfectant level is maintained
(residual free chlorine) do not suffer from MIC.
Water composition, systems design,
commissioning, and on-going compatible
operating conditions are all critical to the
development and retention of protective
films, and long term satisfactory performance
of copper.
Figure 6.1
MIC Corrosion – Cold Water
Hydraulic Services Design Guide - 5 th Edition March 2022
Chapter Six
44
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