Environmental Engineering Reference
In-Depth Information
Figure 3.24
(a) Layer-type (uniform) and (b) plug-type dezincification of brass pipe.
hydroxyl ions (Eq. 2.11). Vacancies, particularly divacancies, are created by
the anodic dissolution.
2.
Diffusion of vacancies into the interior of the alloy, thereby aiding in diffu-
sion of zinc.
3.
Diffusion of zinc in the opposite direction.
Objections to this mechanism have been raised as the diffusion of zinc seems
to be too slow to account for the relatively rapid rate of penetration observed.
The redeposition mechanism seems to derive support from the beneficial effect
of alloying additions of Sn, As, Sb, and P against dezincification in
brass.
Apparently, these elements are redeposited on the alloy as a film and thereby
α
