## 3 Results and Discussion
### Summary of Results  
The conducted experiments underscore the critical influence of deposition time and degreasing temperature on the formation of the coating layer during cataphoretic painting (KTL). The results consistently demonstrate that, as the KTL time increases, the layer thickness rises, reaching peak values at longer deposition durations. Specifically, at a deposition time of 7 min, the maximum thickness is achieved, whereas shorter times, such as 3 min, result in thinner coatings. The impact of voltage is equally significant; at 300 V, the layer thickness increases more steeply, with minimal reduction over time, suggesting that higher voltages promote a greater accumulation of material, particularly in the early deposition stages. The role of degreasing temperature in determining the final layer thickness is also evident. Lower degreasing temperatures, such as 40 \({}^{\circ}\)C, are associated with higher thicknesses, especially for shorter deposition times, whereas higher temperatures, such as 80 \({}^{\circ}\)C, yield reduced thicknesses under identical conditions. This trend suggests that lower temperatures enhance the coating formation process by altering surface properties or interface interactions. Furthermore, intermediate degreasing temperatures, such as 60 \({}^{\circ}\)C, provide an optimal balance between temperature and voltage conditions, leading to more consistent layer thicknesses across varying deposition times. A comparison between experimental results and model predictions further validates these findings. The experimental measurements indicate a significant dependency of layer thickness on deposition time, applied voltage, solution concentration, and temperature. For instance, at 300 V and a deposition time of 7 min, the maximum thickness reaches 22.56 \(\upmu\)m, while at 200 V under the same conditions, the thickness reduces to 18.43 \(\upmu\)m. These results confirm that deposition time and voltage are the primary determinants of layer thickness. The statistical model corroborates these experimental observations, explaining approximately 75% of the variability in layer thickness, with an adjusted coefficient of determination (R\({}^{2}\)) of 70.79%. The model was found to be statistically significant (\(p<0.0001\)), highlighting its reliability in describing the relationship between key process parameters and the resulting layer characteristics. Notably, while solution concentration and degreasing temperature influence layer thickness, their effects are secondary compared to deposition time and voltage. This aligns with the model's predictive accuracy, as evidenced by the minimal deviations between experimental data and model estimates. The comparison of experimental and predicted layer thicknesses (Figure 16) shows systematic differences between model and real values. At a voltage of 200 V and a degreasing agent concentration of 15 g: L\({}^{-1}\), the measured thickness at 3 and 5 min was lower than predicted, with differences ranging from 1.2558 \(\upmu\)m to 2.4514 \(\upmu\)m. At 4 min the measured value was slightly higher than predicted (0.3624 \(\upmu\)m), while at 7 min, it was again lower (2.2809 \(\upmu\)m). At 250 V, shorter times (3-5 min) showed that the measured thickness was always lower than predicted, with differences around 2 \(\upmu\)m. At 6 min, there was an increase in measured thickness above the predicted value (+1.6378 \(\upmu\)m), but at 7 min, the difference was the largest (\(-\)3.0906 \(\upmu\)m), indicating a possible inaccuracy of the prediction model at longer times. At 300 V, the measured thickness was always lower than the predicted thickness at 3-5 min, with differences ranging from 2.0351 \(\upmu\)m to 2.7950 \(\upmu\)m. At 6 min, there was a significant increase in thickness above the predicted value (+2.8805 \(\upmu\)m), but at 7 min, it was again lower than predicted (\(-\)1.7219 \(\upmu\)m).