## 2 Results and Discussion
### Electrochemical Corrosion Measurement  
#### 2.3.1 Potentiodynamic Polarization (PDP) Measurement  
PDP analysis was used for quantitative measurements of the inhibition efficiency (IE) of WPU-g-BTA-A, WPU-g-BTA-B, and WPU-g-BTA-C coatings under 3.5 wt% NaCl environment for 30 min and three days respectively. Short Term Corrosion Study (30 Min)  
The thickness of the coating was set at 060 \(\pm\) 2 \(\upmu\)m. The Tafel plots for the uncoated and coated CRS are presented in Figure 3 and the kinetic corrosion parameters including corrosion potential (Ecorr), corrosion current density (icorr), and IE (%) are summarized in Table 2. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Sample Code**} & \multicolumn{1}{c}{**WPU-g-BTA-A**} & \multicolumn{1}{c}{**WPU-g-BTA-B**} & \multicolumn{1}{c}{**WPU-g-BTA-C**} \\ \hline \multirow{6}{*}{Gel content} & Tube (g) & 13.7608 & 13.7386 & 13.7784 \\  & Sample (g) & 0.6671 & 0.6675 & 0.6674 \\  & THF (g) & 20.171 & 20.0265 & 20.0255 \\  & After drying (g) & 13.8513 & 13.864 & 13.9231 \\  & Gel Content & 13.57 & 18.79 & 21.68 \\  & (\%) & & & \\ \hline Gas permeability & O\({}_{2}\) (barrer) & 1.758322 & 1.045648 & 0.984704 \\ \hline \multirow{2}{*}{Thermal Stability} & T\({}_{\text{d}}\)(5\%) & 252.75 & 257.47 & 257.47 \\  & T\({}_{\text{d}}\)(10\%) & 288.26 & 292.41 & 295.69 \\  & Char yield \% & 3 & 1.6 & 0.21 \\ \hline \multirow{6}{*}{DMA} & Stress & \multirow{2}{*}{51.19} & 47.56 & 50.41 \\  & (kgf/cm\({}^{2}\)) & & & \\ \cline{1-1}  & Elongation (\%) & & & \\ \cline{1-1}  & 100\% modulus & & & \\ \cline{1-1}  & (kgf/cm\({}^{2}\)) & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Gel content, O\({}_{2}\) permeability, and thermal stability measured from TGA and DMA results of WPU-g-BTA coatings. Figure 3: Tafel plots for raw CRS electrode and CRS electrode coated with WPU\(-\)g\(-\)BTA\(-\)A, WPU\(-\)g\(-\)BTA\(-\)B, and WPU\(-\)g\(-\)BTA\(-\)C, in 3.5 wt% NaCl(\({}_{\text{aq}}\)) for 30 min immersion. The inhibition efficiency (IE) of the as-prepared coatings was calculated using Equation (1) [15]:  
\[ \begin{split}\mathrm{i_{corr}(0)-i_{corr}(i)\ \times 100}\\ \mathrm{i_{corr}(0)}\end{split}  \tag{1}\]  
where \(\mathrm{i_{corr}(0)}\) and \(\mathrm{i_{corr}(i)}\) denote the corrosive current densities for the uncoated and coated CRS electrodes, respectively. Ecorr and icorr are substantial parameters that measure the tendency for corrosion and corrosion inhibition as the corrosion rate is directly proportional to Ecorr and inversely proportional to icorr. Thus, the coating with the lowest icorr and the highest Ecorr exhibited the best anticorrosive performance. The coated CRS electrode demonstrated better corrosion protection than the uncoated sample (Figure 3). The Ecorr and icorr values of the uncoated CRS (black curve) were \(-0.811\) V and \(71.77\)\(\mu\)A.cm\({}^{-2}\), respectively. The icorr value decreased (\(0.079\)\(\mu\)A.cm\({}^{-2}\)) in WPU-g-BTA-A (red curve), which exhibited excellent barrier property. With respect to CRS, a drastic shift in Ecorr to more positive potential (\(-0.3311\) V) was observed. The Ecorr value for WPU-g-BTA-B was further moved to \(-0.252\) V with a smaller icorr value of \(0.068\)\(\mu\)A.cm\({}^{-2}\) (green curve). Eventually, CRS coated with WPU-g-BTA-C (blue curve) exhibited a very low icorr value of \(0.020\)\(\mu\)A.cm\({}^{-2}\), which is about 4 and 3.4 orders of magnitude lower than those of WPU-g-BTA-A and WPU-g-BTA-B, respectively. However, the Ecorr for the coating was \(-0.1983\) V, which is more positive than that of WPU-g-BTA-A and WPU-g-BTA-B. Hence, CRS coated with WPU-g-BTA blocked the diffusion of electrolytes. The results indicated that the corrosion inhibition performance of WPU-g-BTA coatings increased with increasing cross-linking density from sample A to C. Overall, CRS-coated samples showed significantly higher corrosion inhibition performance than bare CRS.