Corrosion behavior of duplex polyaniline/epoxy coating on mild steel in 3% NaCl

Abstract

The corrosion behavior and thermal stability of epoxy coatings electrodeposited on mild steel and on mild steel with electrochemically deposited polyaniline (PANI) film were investigated by electrochemical impedance spectroscopy (EIS) and thermo gravimetric analysis (TGA). The aim of the paper was to present new findings on the corrosion protection of mild steel by a duplex PANI/-epoxy coating in 3% NaCl solution and to determine the effect of thin PANI film on the protective properties of the coating. PANI film was deposited electrochemically on mild steel from an aqueous solution of 0.5 mol dm-3 sodium benzoate and 0.1 mol dm-3 aniline at a constant current density of 1.5 mA cm-2. Non-pigmented epoxy coatings on mild steel and on mild steel with PANI film were obtained by cathodic electrode position at constant voltage and stirring conditions. The resin concentration in the electrode position bath was 10 wt.% solid dispersion in water at pH 5.7. The applied voltage was 250 V, the temperature 26°C and the deposition time 3 min. It was shown that thin PANI film could be used to modify the surface of mild steel prior to epoxy coating deposition, due to the increased corrosion protection of a duplex PANI/epoxy coating comparing to an epoxy coating on mild steel in 3% NaCl solution.

Koroziono ponašanje i termička stabilnost epoksidnih kataforetskih prevlaka na mekom čeliku i mekom čeliku sa elektrohemijski taloženim polianilinom (PANI) ispitivani su primenom metoda spektroskopije elektrohemijske impedancije i termogravimetrijske analize. PANI film na mekom čeliku je dobijen elektrohemijskim taloženjem iz vodenog rastvora 0,5 mol dm-3 Na-benzoata I 0,1 mol dm-3 anilina pod galvanostatskim uslovima, gustinom struje od j = 1,5 mA cm-2. Epoksidne prevlake na mekom čeliku I mekom čeliku sa PANI dobijene su elektroforetskim taloženjem u uslovima konstantnog napona uz mešanje. Pokazano je da dvoslojna PANI/epoksidna prevlaka na mekom čeliku ima značajno veću korozionu stabilnosti u 3% rastvoru NaCl u odnosu na epoksidnu prevlaku.