Beijing Technology and Business University "JAC": One-step method to form a composite electropolymer protective coating on the copper surface!

Copper alloys are widely used in many manufacturing fields such as industrial heat exchange and electronic device assembly due to their good ductility and thermal/electrical conductivity.
However, harsh environments (such as Cl-containing media) can damage the passivation film on the copper surface, and then erode the metal substrate, seriously threatening the performance and life of related facilities.
Electropolymerization (ECP) can form a thin layer of conductive polymer in situ on the metal surface, and through the anodic protection and physical shielding equivalent to play an excellent protective effect on the substrate com" href="">coating online coatingol.
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Under normal circumstances, the active metal surface must undergo a passivation link before forming an electropolymerized coating by ECP to provide a steady-state interface, which indirectly limits the in-situ occurrence and functional advantages of ECP.

In view of this, Fan Baomin and others from Beijing Technology and Business University introduced tonn salt to form a poly(N-methylaniline)/sodium phosphate long-term protective ECP layer on the copper surface in one step, which can achieve in-situ repair of the damaged coating; in multi-scale theory Based on the simulation, the concept of using the time-domain spatial diffusion trajectory to evaluate the protective performance of the coating is put forward.

Under different interaction addition terms (electrostatic force and van der Waals force), the visual description of the specific tracing target in the coating at different stages Diffusion behavior, and then obtain the failure mechanism of the coating service process.

Link to the paper: https://doi.

org/10.

Through the electrochemically easy-to-operate ion doping process, different contents of sodium phosphate (1 mM, 5mM, 10 mM) are doped into the N-methylaniline solution, and the poly(N-methyl) is formed in situ on the copper surface in one step.

Base aniline)/sodium phosphate electropolymer composite coating.

The morphology and electrochemical analysis of the coatings immersed in 3.

5% NaCl solution for different lengths of time were carried out.

Figure 1 The morphology of different coatings before and after immersion in corrosive medium for 30 days

Figure 2 Potential polarization curves of the coating under different immersion time

Figure 3 Electrochemical impedance spectra of the coating under different immersion time

Multi-scale theoretical calculations show that the phosphate is stabilized between the PNMA chains by electrostatic force and promotes the parallel deposition of polymers on the copper surface.

The time-domain spatial diffusion trajectories of in-situ ions show that there are differences in the diffusion behavior of corrosive ions in the two models: the corrosive ions in PNMA have an expanded diffusion trajectory, showing a tendency to migrate across the coating; while the in-situ in the composite coating Ions are restricted to move in a local area.
The composite coating hinders the diffusion of ions and slows down the transmission of ions inside the coating, which significantly inhibits the corrosion of the metal by the corrosive medium, which is consistent with the experimental results.
The composite coating benefits from a dense structure, good barrier and anode protection to provide excellent long-term protection for the substrate.

Figure 4 The equilibrium configuration of polymer chains in the PNMA and PNMA-5P models and the radial distribution function of characteristic atoms

Figure 5 Time-domain spatial diffusion trajectories of in-situ ions in PNMA and PNMA-5P coatings