PSI - Issue 36

Tetyana Kalyn et al. / Procedia Structural Integrity 36 (2022) 313–317

315

3

T. Kalyn, L. Poberezhny, P. Popovych et al. / Structural Integrity Procedia 00 (2021) 000 – 000

rate was 50 mV/s. Testing was performed using a trielectrode electrochemical cell with a volume of 250 ml. The working electrode was made of the 17H1S steel with an exposed to solution area of 0.03 cm 2 , the reference electrode was silver chloride electrode, the auxiliary electrode was graphite. The inhibitor AA was added into the test solution. The effect of inhibition IE e was determined by the formula:

I

I

−

(3)

( )

corr bl

corr

(%)

%

IE

100

=



I

( )

corr bl

where I corr (bl ) and I corr – corrosion current density of steel in test solution without and with inhibitor, respectivelly. 3. Results and discussion Results of weight loss studies of corrosion protection of the steel in the NS4 test solution by AA with various concentrations are presented in Table 2. As can be seen from the results, the inhibitory effect of AA increases at increasing concentration from 0.1 to 1.0 g/l and decreases at a concentration of 1.5 g/l.

Table 2. Values of protective effects for AA solutions of different concentrations Concentration of AA, g/l IE w , % IE e , % 0.1 8.06 12.09 0.2 40.10 41.92 0.4 58.69 63.35 0.75 73.80 74.05 1.0 80.95 88.41 1.5 75.21 77.81

Before potentiodynamic measurements, the potential vs time dependences of the pipeline steel in the NS4 solution without and with the addition of AA were recorded. As shown in Figure 1, a significant positive shift of the open circuit potential was revealed at adding the inhibitor into the solution, especially at a concentration of AA of 1.0 g/l. The open circuit potential values of the investigated steel were more positive for all studied concentrations of AA compared with the unhibited NS4 solution. Gonçalves et al. (2001) noted an increase in the corrosion potential by 100 mV for a 0.5M sodium sulfate solution in the presence of AA, which was associated with the adsorption of AA on the active areas of the electrode surface and blocking the adsorption of water molecules. According to Ferreira et al. (2004) AA is a mixed-type inhibitor at concentrations of up to 10 -3 mol/l in acidic solutions.

Fig. 1. Potential vs time dependence of steel 17H1S in NS4 medium without and with addition of AA.