Page 19 - Vol_1_Chapter_VI

Fig. 6. 13 SEM images of shot-peened samples under the shot-peened surface (a), at the core of the
25
material(b) and under the non-shot-peened surface (c)

6.7 Galvanization

Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to
prevent rusting. The most common method is hot-dip galvanizing, in which the parts are coated by
submerging them in a bath of hot, molten zinc. 26
The zinc coating, when intact, prevents corrosive substances from reaching the underlying iron.
Additional electroplating such as a chromate conversion coating may be applied to provide further
surface passivation to the substrate material. 27

Process description
Depositing a thick, robust layer of zinc iron alloys on the surface of a steel product is known as hot-dip
galvanizing. For the usage in the automotive industry, such as the case of car bodies, which are going
to get painted by decorative coatings, a thinner layer of zinc coating is applied by electrogalvanizing.
The hot-dip process generally does not reduce strength to a measurable degree, with the exception of
high-strength steels where hydrogen embrittlement can become a problem.
Thermal diffusion galvanizing, or Sherardizing, provides a zinc diffusion coating on iron- or copper-
based materials (Fig. 6. 14). 28

Copyright © by DIGIGREEN All Rights Reserved Volume I - Chapter VI: Digital and Green Surface Conditioning 19