Sodium dodecyl sulfate (SDS) as an effective corrosion inhibitor for Mg-8Li-3Al alloy in aqueous NaCl: A combined experimental and theoretical investigation

The corrosion inhibition behavior of Mg-8Li-3Al alloy in NaCl solution with sodium dodecyl sulfate(SDS)was investigated by hydrogen analysis,scanning electron microscopy(SEM),electrochemical test,scanning Kelvin probe force microscopy(SKPFM)and computational methods.Results showed that the corrosion resistance of Mg-8Li-3Al alloy in NaCl solution was effectively improved with SDS.The SEM and SKPFM results confirmed a dense,200 nm-thick SDS-adsorbed layer had formed on the alloy surface.The separation energy ΔE_(gap) and adsorption energy E_(ads) of SDS on the Mg surface were calculated by density functional theory and molecular dynamics simulations,respectively.And the corrosion inhibition mechanism was hypothesized and described.

Quantitative micro-electrochemical study of duplex stainless steel 2205 in 3.5wt%NaCl solution

Duplex stainless steels(DSSs)are suffering from various localized corrosion attacks such as pitting,selective dissolution,crevice corrosion during their service period.It is of great value to quantitatively analyze and grasp the micro-electrochemical corrosion behavior and related mechanism for DSSs on the micrometer or even smaller scales.In this work,scanning Kelvin probe force microscopy(SKPFM)and energy dispersive spectroscopy(EDS)measurements were performed to reveal the difference between the austenite phase and ferrite phase in microregion of DSS 2205.Then traditional electrochemical impedance spectroscopy(EIS)and potentiodynamic polarization(PDP)tests were employed for micro-electrochemical characterization of DSS 2205 with different proportion phases inϕ40 andϕ10μm micro holes.Both of them can only be utilized for qualitative or semi-quantitative micro-electrochemical characterization of DSS 2205.Coulostatic perturbation method was employed for quantitative micro-electrochemical characterization of DSS 2205.What is more,the applicable conditions of coulostatic perturbation were analyzed in depth by establishing a detailed electrochemical interface circuit.A series of microregion coulostatic perturbations for DSS 2205 with different proportion phases inϕ10μm micro holes showed that as the austenite proportion increases,the corresponding polarization resistance of microregion increases linearly.

Influence of Micro/Nano-Ti Particles on the Corrosion Behavior of AZ31-Ti Composites

Adding Ti particles to magnesium alloy simultaneously enhances its strength and ductility.However,how these particles influence on Mg alloy’s corrosion performance is seldom reported.The corrosion behavior of AZ31-Ti composites containing titanium nanoparticles(1.5 and 5 wt%)and micron particles(10 wt%)prepared by powder metallurgical in 3.5 wt%NaCl solution was investigated.The results indicate that Ti particles serve as the primary location for the cathodic hydrogen reduction reaction,resulting in intense galvanic corrosion between the Ti and Mg matrix.Ti nanoparticles distributed at the interface of the original AZ31 powder were in a discontinuous mesh structure,thus failing to act as a barrier against corrosion.The corrosion products with the existence of numerous cracks gradually peel off during the corrosion process and cannot protect the matrix.The average corrosion rate P_(w) of AZ31,AZ31-1.5%Ti,AZ31-5%Ti,and AZ31-10%Ti after 7 days of immersion is 27.55,105.65,283.67,and 99.35 mm/y,respectively.Therefore,AZ31-Ti composites can be considered as potential candidates for degradable fracturing tools.Otherwise,it is recommended to improve their corrosion resistance through surface treatment.

Quasi-in-situ Observation and SKPFM Studies on Phosphate Protective Film and Surface Micro-Galvanic Corrosion in Biological Mg-3Zn-xNd Alloys

The phosphate protective film and micro-galvanic corrosion of biological Mg-3Zn-xNd (x = 0, 0.6, 1.2) alloys were investigated by scanning and transmission electron microscopy, quasi-in-situ observation, scanning Kelvin probe force microscopy (SKPFM) and electrochemical tests. The results revealed the Mg-Zn-Nd phases formed in Mg-3Zn alloy contained with Nd. Adding Nd resulted in a significant decline in the cracks of the phosphate protective film and micro-galvanic corrosion of alloys, which were recorded by quasi-in-situ observation. In addition, the Volta potential difference of Mg-Zn-Nd/α-Mg (~ 188 mV) was lower than MgZn/α-Mg (~ 419 mV) and Zn-rich/α-Mg (~ 260 mV), and the corrosion rates of alloys markedly decreased after the addition of 0.6 wt% Nd. The improvement in corrosion resistance of Nd-containing alloys was mainly attributed to the following: (i) the addition of Nd reduced the Volta potential difference (second phases/α-Mg);(ii) the phosphate protective film containing Nd_(2)O_(3) deposited on the surface of the alloys, effectively preventing the penetration of harmful anions.

A dual-use probe for nano-metric photoelectric characterization using a confined light field generated by photonic crystals in the cantilever

We propose a plasmonic atomic force microscopy (AFM) probe, which takes a part of the laser beam for monitoring cantilever deflection as the excitation light source. Photonic crystal cavities are integrated near the cantilever’s free end where the laser spot locates. The transmitted light excites surface plasmon polaritons on the metal-coated tip and induces a confined hot-spot at the tip apex. Numerical simulations demonstrate that the plasmonic probe can couple a tilted, linearly polarized beam efficiently and yield a remarkable local electromagnetic enhancement with the intensity being around 21 times stronger than that of the original probe. For demonstration, we employ the plasmonic probe in electrostatic force microscopy and scanning Kelvin probe microscopy to study the impact of local light field on the photoelectric characteristics of SiO_(2) and Au nanoparticles. Compared with the original probe, obvious differences are observed in the electrostatic force gradients on SiO_(2) nanoparticles and in the surface potentials of Au nanoparticles. The plasmonic probe can enable AFM as a powerful tool for simultaneous optical, mechanical and electrical characterizations.