Electrochemical behaviors of magnesium alloy with phosphate conversion coating in NaCl solutions

Abstract

A composite conversion coating was prepared on magnesium alloy by the only one-step immersion treatment. The characteristics of the conversion coating were investigated by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicate that the composite conversion coating consists of magnesium hydroxide, magnesium phosphate and manganese phosphate. The electrochemical behavior of the conversion coating was investigated systematically by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurement in different NaCl solutions. Polarization measurements and EIS results reveal that the magnesium alloy with the conversion coating have better corrosion resistance compared to the bare magnesium alloy in these conditions. And the corrosion rate of the magnesium alloy with conversion coating increases consistently with the chloride ion concentration. In alkaline conditions, the magnesium alloy with conversion coating has superior corrosion resistance by the synergistic effects between Mg(OH) 2 film and conversion coating. Moreover, the electrochemical corrosion mechanism of the magnesium alloy was analyzed with respect to the conversion coating in a Cl -containing environment.

Fabrication of Green and Scalable N/P/S/Mn Containing Biobased Layered Double Hydroxide as a Novel Flame Retardant and Efficient Char Forming Agent for Polypropylene

“…Moreover, elements Mg, Al, C, O, S, N, P, and Mn appeared in the XPS spectra of LDH-LS@CS@PAMn with atomic percentages of 10.78, 6.47, 21.45, 47.28, 0.41, 1.21, 8.95, and 3.45%, respectively, with peaks appearing at 135.4 and 642.3 eV corresponding to P 2p and Mn 2p of PAMn in LDH-LS@CS@PAMn, respectively. , As displayed in Figure B–F, N 1s, O 1s, S 2p, P 2p, and Mn 2p high resolution spectra of LDH-LS@CS@PAMn can be deconvoluted into three, three, two, four, or two peaks. In the O 1s spectra (high resolution) of LDH-LS@CS@PAMn, the peaks of 530.7, 531.8, and 533.0 eV correspond to the O–Mn, C–O, and phosphate structures. , In the N 1s spectra (high-resolution), the peaks at 399.4, 400.7, and 402.5 eV belonged to C–N, −NH 2 , and NH 3+ , respectively. , It was demonstrated that the partial amino group in CS was successfully protonated in the PA solution and self-assembled with PA by hydrogen bonding and electrostatic interaction. Surely, there was no doubt that peaks of phosphate/hydrogen phosphate (133.6 eV) and manganese phosphate (134.5 eV) were present in the P 2p high-resolution spectra of LDH-LS@CS@PAMn. , In the S 2p high-resolution spectrum of LDH-LS@CS@PAMn, peaks of 165.1, 163.8, 167.6, and 168.9 eV appeared, which respectively correspond to C-S 2p 1/2 , C-S 2p 3/2 , SO 3 2– 2p 3/2 , and SO 3 2– 2p 1/2.…”

“…In the O 1s spectra (high resolution) of LDH-LS@CS@PAMn, the peaks of 530.7, 531.8, and 533.0 eV correspond to the O−Mn, C−O, and phosphate structures. 49,50 In the N 1s spectra (highresolution), the peaks at 399.4, 400.7, and 402.5 eV belonged to C−N, −NH 2 , and NH 3+ , respectively. 31,49 It was demonstrated that the partial amino group in CS was successfully protonated in the PA solution and self-assembled with PA by hydrogen bonding and electrostatic interaction.…”

Formation and corrosion resistance of a novel Co–Ti–Mo composite chromium‐free chemical conversion coating on LY12 aluminum alloy

“…Then, the EIS data is also fitted by electrical equivalent circuit, and the suitable R(C(R(CR))) Randle equivalent circuit model (ECM) was selected and displayed in Figure 6. In the ECM, R s is the solution resistance; R f is the film resistance, in parallel with a constant phase element (CPE f ); R ct is the charge transfer resistance on the metal surface, in parallel with a constant phase element (CPE dl ) [ 26 ] . The relating parameters of ECM used in the fitting procedure are presented in Table 3.…”

Preparation of Mn2+ Doped Piperazine Phosphate as a Char-Forming Agent for Improving the Fire Safety of Polypropylene/Ammonium Polyphosphate Composites

“…In the Mn 2p high resolution spectrum of HP-Mn (Figure 2d), the peak can be deconvoluted into three peaks at 641.2 eV (Mn 2p 3/2 ), 653.6 eV (Mn 2p 1/2 , manganese(II) phosphate), and 645.3 eV (satellite peak of Mn 2p 3/2 ) [34,35]. The peaks of P 2p high resolution spectrum (Figure 2e) at 132.1 eV and 133.2 eV correspond to manganese phosphate and phosphoric acid/hydrogen phosphate [36,37]. In the O 1s high resolution spectrum (Figure 2f), the peak at 532.2 eV is ascribed to phosphate, while the signals at 531.5 eV and 530.4 eV are attributed to the -OH and O-Mn, respectively [38].…”