Corrosion Protection Evaluation of Copper Coated with a Block Copolymer and Block Coploymer/Carbon Black Nanoparticles in 3 wt% NaCl Solution

Abstract

This paper presents a successful preparation of SEBS (a copolymer polystyrene‐block‐poly (ethylene‐ran‐butylene)‐block‐polystyrene) and SEBS‐CB (SEBS‐Carbon Black nanoparticles) coatings on a copper surface following a well‐defined immersion protocol. Such coatings′ protection capacity was tested in a 3 wt% NaCl medium using potentiodynamic polarization, cyclic voltammetry (CV), and electrochemical impedance techniques (EIS). The electrochemical measurements indicate that SEBS and SEBS‐CB are cathodic‐type inhibitors mainly hindering the diffusion of oxygen molecules toward the copper substrate. It also indicates the decrease in chloride ion attack on the coated copper layer. Not only that, but it also affirms the decrease in CuCl2- ${{{\rm \ }{\rm C}{\rm u}{\rm C}{\rm l}}_{2}^{-}}$ ‘s transport to the bulk solution, resulting in our sample being further protected at more positive potential. Cu‐SEBS‐CB electrodes showed a slight improvement in corrosion protection compared to Cu‐SEBS electrodes. π‐π stacking was associated with improving the performance of these coatings. The keys functions of incorporating CB are improving the electrode conductivity and having a denser and more compact coating than that without CB. The order of inhibition efficiency obtained by potentiodynamic polarization is in good agreement with the results achieved by electrochemical impedance spectroscopy. Also, the inhibition efficiency of Cu‐SEBS and Cu‐SEBS‐CB increases with increasing the ratio of SEBS. Adsorption of SEBS and SEBS‐CB on copper surface follows the Langmuir isotherm.

Corrosion Evaluation of Copper with Polystyrene‐Block‐Poly(ethylene‐ran‐butylene)‐Block‐Polystyrene Triblock (SEBS) Copolymer Coating in 3 % NaCl Solution by Using Response Surface Methodology

“…Such results are in good agreement with the previous study which we found that SEBS is a cathodic-type inhibitor. [24] These results lead to the conclusion that this coating film effectively retards the cathodic oxygen reduction, and thus protects the copper from corrosion. Therefore, the corrosion process significantly affects the cathodic polarization curve of bare copper.…”

“…[24,51] The Warburg impedance in the low frequency region is ascribed to the diffusion process of the soluble copper species from the electrode surface to the bulk solution and the diffusion of dissolved oxygen from the bulk solution to the electrode surface. [24,52] The Nyquist plot of Cu-SEBS-Opt-Cond is fairly distinct from that of the bare copper electrode. For the SEBS-coated copper electrode at, the Warburg impedance disappeared, indicating that the film is amply densely packed to prevent the diffusion of oxygen or Cl À ions to the copper substrate and thus inhibits the corrosion of copper.…”

“…The smaller value of n becomes, the rougher the surface becomes and the more serious the corrosion becomes. [24] For an excellent fitting and for the general accuracy evaluation of the fit, we made use of three basic criteria: visual fit to Bode and Nyquist plots, low goodness of fit, and low relative standard errors for every circuit element. [45] We obtained suitably low goodness of fit (< 10 À 3 ) and the error linked to each element was lower than 10 %.…”

“…We noticed that the bare copper had 3 anodic peaks in the forward scan and a reduction peak and an anodic current hump in the reverse scan. [24] The first peak is identified by the formation of a soluble cuprous chloride complex, CuCl À 2 , and the second anodic peak emanates from the formation of cuprous oxide (Cu 2 O). [24] The third oxidation peak is characterized by the oxidation of Cu 2 O to cupric oxide (CuO) and cupric hydroxide (Cu(OH) 2 ).…”

“…The adsorption behavior of SEBS on the copper surface is in accordance with the Langmuir adsorption isotherm and the values of the standard free energy indicate that their adsorption mechanism was mixed-type adsorption. [24] The materials' corrosion rate depends on various conditions, such as the concentration of coating, immersion time, temperature, pH of solution… It is trusty to note that classical methods (the univariate methods) where only one of the evaluated parameters is varied while the others are kept constant, do not depict the combined effect of all the factors involved. The univariate methods are empirical ones that are incapable of measuring the synergic and antagonistic interactions.…”