The present study demonstrated that the coloring
method for stainless steels proposed by Ogura et al. [10]
is indeed applicable to commercial stainless steels of the
AISI-304 type. The oxide films grown electrolytically on
Acesita’s AISI-304 # 2B stainless steel presented a good
adherence. The uniformity and brightness of their colors
were strongly dependent on the steel surface polishing
and also on its grain size. The spectral reflectance
technique proved to be useful to clearly define the
colors of the oxide films and also to estimated their
thicknesses. The electrolysis of the stainless-steel sam-
ples at the potential amplitudes of 0.41, 0.42 and 0.43 V
lead to oxide films whose thicknesses increased (80/370
nm) linearly with the electrolysis time (10/50 min). The
thickness of the oxide films grown at the potential
amplitude of 0.44 V did not vary significantly as the
electrolysis time was increased, presenting values in the
range 120/200 nm.
The corrosion rates for the oxide films grown at the
different potential amplitudes (0.41/0.44 V) and elec-
trolysis times (10/50 min) were always lower than those
for non-electrolysed stainless steel (1.49/0.2 mm/year).
Among the electrolysed steel samples, the oxide films
grown at the potential amplitudes of 0.42 and 0.44 V
presented the best protection properties against uniform
corrosion, increasing the service life of the substrate by
up to eight times.
Finally, the susceptibility to pitting corrosion was
practically the same for electrolysed and non-electro-
lysed steel samples. For the electrolysed steel samples,
all the (Epit/Ecor) values seem to tend to 0.159/0.05 V
for longer electrolysis times; this same value was also
observed for non-electrolysed steel samples.
The present study demonstrated that the coloringmethod for stainless steels proposed by Ogura et al. [10]is indeed applicable to commercial stainless steels of theAISI-304 type. The oxide films grown electrolytically onAcesita’s AISI-304 # 2B stainless steel presented a goodadherence. The uniformity and brightness of their colorswere strongly dependent on the steel surface polishingand also on its grain size. The spectral reflectancetechnique proved to be useful to clearly define thecolors of the oxide films and also to estimated theirthicknesses. The electrolysis of the stainless-steel sam-ples at the potential amplitudes of 0.41, 0.42 and 0.43 Vlead to oxide films whose thicknesses increased (80/370nm) linearly with the electrolysis time (10/50 min). Thethickness of the oxide films grown at the potentialamplitude of 0.44 V did not vary significantly as theelectrolysis time was increased, presenting values in therange 120/200 nm.The corrosion rates for the oxide films grown at thedifferent potential amplitudes (0.41/0.44 V) and elec-trolysis times (10/50 min) were always lower than thosefor non-electrolysed stainless steel (1.49/0.2 mm/year).Among the electrolysed steel samples, the oxide filmsgrown at the potential amplitudes of 0.42 and 0.44 Vpresented the best protection properties against uniformcorrosion, increasing the service life of the substrate byup to eight times.Finally, the susceptibility to pitting corrosion waspractically the same for electrolysed and non-electro-lysed steel samples. For the electrolysed steel samples,all the (Epit/Ecor) values seem to tend to 0.159/0.05 Vfor longer electrolysis times; this same value was alsoobserved for non-electrolysed steel samples.
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