byB.LALITHAMANI

Lecturer, Department of Chemistry,Sri Ramakrishna Engineering College

Coimbatore

CORROSION INHIBITION OF FLUOROQUINOLONE DERIVATIVES ON MILD

STEEL IN VARIOUS CORROSIVE MEDIA

Under the guidance ofDr. M. KUMARAVEL

Assistant Professor and Head,Department of Chemistry,

PSG College of TechnologyCoimbatore

SIGNIFICANCE OF CORROSION STUDIES Increasing use of metals in all fields Use of rare and expensive metals Increasing pollution of air and water resulting in a more

corrosive environment Use of high strength alloys that gets corroded easily

CORROSION CONTROL MEASURESThere are four basic methods for Corrosion Control &

Corrosion Protection. Materials resistant to corrosion Protective coatings Cathodic protection Corrosion Inhibitors- Modify the operating environment.

Non electrochemical methodsElectrochemical and

special methods

Non-destructive

testing methods

Weight

loss

method

Gasometri

c method

Electrical

resistance

method

Linear polarization

method

Potential

measureme

nts

Polarization

measurements

Impedance

measurements

Ultrasoni

c's

Eddy current

method

Radiographi

c method

Fluoroquinoline derivatives are a class of antibiotics and the important members include ciprofloxacin, ofloxacin, leavofloxacin,. Etc.

They contain nitrogen and other hetero atoms in their structures and are expected to have corrosion inhibition efficiencies.

Hence the objective of the work is to isolate the active ingredients from the floxacin drugs and study the corrosion inhibiting action on mild steel in various corrosive media by adopting different corrosion monitoring techniques such as weight loss method, impedance spectroscopy, potentiodynamic polarization etc.,

Mild steel coupons of dimensions 2.5cm X 1cm X 0.1cm

having the compositions 0.084%C, 0.037%Mn, 0.026%P,

0.021%S and the remaining being Fe can be used for weight

loss studies. The mild steel coupons are polished mechanically using

emery papers of grades 220, 400, 600, 800 and 1200 then

washed thoroughly with double distilled water. Finally, the specimens are rinsed in acetone and dried. A Teflon coated mild steel rod of area 0.19625cm2 and

having the composition same as that of the coupons can be

used for both impedance and potentiodynamic polarization

studies. The inhibitor solutions are prepared in 1NHCl and INH2SO4

acid solutions.

WEIGHT LOSS METHODThe mild steel specimens in triplicate were immersed for

different time periods in 100ml of corrosion media with and

without inhibitors at room temperature. The specimens are weighed before and after immersion

and the average of weight loss of three specimen are used

to find out the inhibition efficiencies.

The inhibition efficiencies are calculated using the formula

w -w’

wl (%) = ------- X 100

w

where w and w’ are the weight losses in the

uninhibited and inhibited solutions

POTENTIODYNAMIC POLARIZATION STUDIES The potentiodynamic polarization curves are recorded using

a there electrode cell arrangement The potentials are swept at the rate of 1.66mVs-1. The potentials are scanned primarily from more negative

potential than EOC to the more positive potential than EOC

through Ecorr.

The inhibition efficiencies are calculated using the

relationship i – i’

IE % = --------- X 100

i where i and i’ are the corrosion current densities in the

absence and in the presence of inhibitor respectively.

IMPEDANCE MEASUREMENTS Electrochemical impedance measurements may be carried

out using a Potentiostat/galvanostat/FRA (PARSTAT 2273-

Princeton Applied Research -USA). Data acquisition is to be done with the help of the dedicated

PowerSuite software and the impedance data may be

analysed using Zsimpwin software (version 3.21). A conventional three electrode set up is employed with a Pt

foil as the auxiliary electrode and a saturated Calomel

electrode as the reference electrode. The mild steel cylinder, with surface preparations done as

mentioned in the weight loss method, served as the working

electrode.

The measurements are carried out in the frequency

range 106 Hz to 10-2 Hz at the open circuit potential, by

applying 10mV sine wave AC voltage. The inhibitor efficiency is calculated as follows

R’ct – Rct

IE % = -------------- X 100

R’ct

Where Rct and R’ct are the charge transfer

resistance values in the uninhibited and inhibited

solutions

The inhibiting efficiency of few quinolone derivatives are to be

studied using the corrosion monitoring techniques. To correlate the structure of the isolated quinoline with inhibition

properties. To establish the mechanism of inhibition To study the mechanism of adsorption on the MS surface To determine the PZC (Potential of Zero Charge) and surface

charge. Also it is proposed to find out novel and eco friendly inhibitors

and judicial combinations of inhibitors for effective corrosion

control.

THANK YOU