الفهرس 
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Abstract
Metallic coating is considered one of the best methods
utilized to minimize corrosion of steel. The most common
coatings are aluminium (aluminizing) and zinc (galvanizing).
The fact that neither aluminium nor zinc provides all
requirements for the different applications, leads
to apply
AI-Zn alloys as coatings on steel. Zn-5% Al ( galfan
) and
55% AI-45 % Zn ( galvalume ) coatings have been already in
use.
The present study was aimed
to
inves tiga te the
effects of coating layer composition, time of hot dipping
and time of heat treatment of coated samples on
their
electrochemical behaviour in 3.5% NaCI solution.
Increase of
in
the coating
layers
Al
conten t
reduces their corrosion intensity; e.g.
i for
COl’ r.
(45/55 )
AI/Zn coating is 0.349 pA/cm2 whereas it is only 0.237 yA/cm2
for (55/45) AI/Zn coating.
Time of hot dipping has little effect on corrosion
characteristics of
the produced coatings;
e.g.
i
cor•r.
for samples hot dipped in (50/50 ) AI/Zn bath~ for 5 seconds
and
seconds
0.335
2
J-1A/cm
0.302
2
}.lA/cm ,
and
30
are
respectively.
Time of heat treatment of coatings has very great
effect on their corrosion characteristics ;e.g. annealing of
(50/50 )AI/Zn
c-
coated samples at 350 C for 36 hrs.
reduces
2 2
i from 0.310 ~A/cm to 0.069 ~A/cm .
corr.