During the electrochemical roughening, mainly iron and
nickel components of the alloy are dissolved, thus leading to
enrichment of the chromium-containing phases in the form
of 1–10mm facets of a Venetian mosaic as shown in Fig. 1a
and b. The facets are separated by macroconcavities having
a depth of the same order. This depth is a function of the
time of anodic roughening.
The structure of chromium oxide layer formed on the steel
surface is presented in Fig. 1c. This picture is observed on
the flat part of the facets after a considerable magnification.
The chromium oxides have small grains. Their sizes range
from 30 to 150 nm.