Metal coupons preparation
samples of dimension 30mm × 20mm × 2mm had been cut from a large sheet of mild
steel. The samples were polished and drilled a hole at one end. During the
experiment, the samples were polished with sandpapers, degreased in acetone,
washed with distilled water, dried and stored in a desiccator in the absence of
moisture before their use for the investigation. Since hydrochloric acid is
widely used for pickling, HCl medium was selected for the study (Thilagavathy & Saratha, 2015).
The sago extract was
weighed to 100g before being soaked together with 100ml of 1.0 mol HCl in a
beaker prior to stock solution. It is advisable to often stir the mixture in
order to prevent the solution hardened with time. From this stock solution,
fixed concentration (dosage = 20ml) of the inhibitor was prepared. The stock
solution was measured to 20ml dosage by using a measuring cylinder before being
poured into every five beaker which filled with 200ml of 1.0 mol HCl. The mixtures
were then heated with room temperature, 30
. The other beaker was solely filled
with 200 ml of 1.0 mol HCl and heated under room temperature.
While the mild steels
were stored in the desiccator, some preparations had been made. The 200ml of
1.0 mol HCl in each six beaker was stirred evenly by using a magnetic stirrer
for several minutes under room temperature. The prepared 20ml dosage stock
solutions were then poured into every five beaker and let solely the other one
beaker to test the inhibition of mild steel with hydrochloric acid without
green corrosion inhibitor under room temperature. The solutions were then heated
according to chosen temperatures individually. The mixtures were left to be
stirred evenly afterwards.
The mild steels in the
desiccator were taken out prior to brushing and cleaning them off with acetone.
The steels were dried and their initial weights were taken by using digital
balance accurately. The cleaned and weighed mild steels were suspended using
glass hooks and rods in the beakers. The experiment was performed under total
immersion conditions of the aerated and continuous stirred solutions. The
measurements were operated at room temperature (with and without inhibitor) and
with inhibitor in the range of (30-60)
for 1 hour. After the elapsed time, the weight
losses were determined with respect to time by retrieving the metals from test
solution, washed, cleaned, dried and reweighed accurately. With the same metals,
the experiment was repeated for 3 hours retention time.
Weight loss measurements
The difference between
the weight of the mild steel at a given time and its initial weight was taken
to be weight loss.
loss (g) = Initial weight – Final weight
Weight loss allowed us
to calculate the corrosion rate as expressed in (g/m2day).
The corrosion rate (Cr)
and inhibitor efficiency, IE (%) were calculated according to the following
equations respectively :
Corrosion rate, where surface
area is 0.0012795 m2 According
to (Arockiasamy et al., 2014) the formula for inhibition efficiency is
= Corrosion rate without inhibitor
= Corrosion rate when inhibitor is