ACl2 NaHCO3 NaCl, HCl, and H2 SOOCP, PDP, and EIS OCP, PDP, and EISCurrent StudyGFRP, KFRP, and pure epoxy25 h2. Resources and Approaches two.1. Elements Cleaned EN10130 carbon steel sheet specimens using a thickness of one.5 mm, length of 8 cm, and width of four cm have been applied because the substrate for epoxy coatings and FRP layers. The chemical composition from the EN10130 carbon steel sheet is given in Table 2. Very first, the specimens were ground applying different abrasive papers, as much as 1200 grits, to improve the epoxy and FRP layer adhesion together with the steel surface and stop delamination. Subsequent, the specimens were washed with water, degreased in acetone, washed again, and dried with air.Table two. Chemical composition from the EN10130 carbon steel sheet. Fe 99.09 C 0.twelve Mn 0.6 P 0.045 S 0.045 Si 0.Four kinds of specimens had been prepared utilizing the hand layup method, as proven in Figure 1. The very first type is often a manage sample, a non-coated steel WZ8040 Autophagy specimen called the exposed substrate. The second kind is definitely the epoxy-coated steel specimen, referred to as epoxy/steel. The third and fourth types are the glass fiber-reinforced polymer and Kevlar fiber-reinforced polymer layers additional towards the steel specimens, referred to as GFRP/steel and KFRP/steel, respectively. The glass fabric (grade GF-22-280-100) and Kevlar material (grade K-22-300-100) are (0 /90 ) woven fabrics produced by Straightforward Composites Ltd. The polymeric matrix comprises a PHA-543613 Protocol hundred elements epoxy resin (EL2) and thirty parts curing agent (AT30). The prepared specimens had been left for 48 h at area temperature to remedy. The average thickness from the epoxy coating and FRP composite layers in all the specimens wasPolymers 2021, 13,four of0.5 mm for each layer. Figure two shows the SEM images with the cross-sections in the ready specimens.Figure one. Ready specimens: (a) GFRP/steel, (b) KFRP/steel, (c) epoxy/steel, (d) non-coated steel.Figure two. Cross-sectional SEM pictures from the prepared specimens.two.2. Techniques Potentiodynamic Polarization (PDP) and Electrochemical Impedance Spectroscopy (EIS) Potentiodynamic polarization testing was utilised to assess the kinetics on the corrosion reactions as well as the corrosion costs and potentials concerning the anodic reactions, the cathodic reactions, and passivity [43]. The potentiodynamic polarization scans were from -1.two V to 0.5 V (SCE). Furthermore, EIS was made use of to quantify the impedance of coatings to corrosion and to assess the interfacial interactions with the coated programs in the resolution interface, across the coating, and near the steel substrate, in accordance to the ASTM-G106 standard [44]. The 4 specimens were immersed in 0.five M NaCl, 0.5 M HCl, and 0.5 M H2SO4 remedies to research their conduct. An EIS examine was carried out at open circuit potentials (OCPs) inside of the frequency variety of 0.2 Hz to one hundred,000 Hz. OCP tests have been carried out to assess the dominance of the anodic reactions versus the cathodic reactions and their variations with time concerning the coating form system as well as environmental conditions. The electrochemical exams had been carried out with the GAMRY 3000 potentiostat, as shown in Figure three.Polymers 2021, 13,5 ofFigure 3. The electrochemical cell setup.3. Results and Discussion three.one. OCP/Potentiodynamic Polarization The samples; the exposed substrate; as well as glass/epoxy, Kevlar/epoxy, and epoxy programs have been immersed for 25 h inside the testing answers of 0.five M NaCl, 0.5 M HCl, and 0.five M H2 SO4 . The open-circuit potentials had been monitored (which include the electrochemical imp.