مجله علوم و مهندسی خوردگی
سال سیزدهم شماره 3 (پیاپی 49، پاییز 1402)

In this study, Ni-WC-TiO2 coating was produced by pulsed current (PC) on St-37 samples (1-5) and by pulsed reverse current (PRC) on samples (6-9). In order to investigate the morphology of the coatings, field emission scanning microscopic (FE-SEM) images were used. The coating resulting from the pulsed reverse current has more uniformity and fineness than the pulsed current. The EDS results showed that Carbon, tungsten, titanium, oxygen and nickel elements were formed on the surface in both plating currents. The anti-corrosion performance of the coatings was investigated through EIS and polarization tests. The analysis of the results of these tests showed the improvement of the anti-corrosion performance of PRC samples compared to PC samples. The results indicated that the presence of WC and TiO2 nanoparticles decreased the Rct (charge transfer resistance) of sample 6, Rct=99.77 (ohm.cm2 ) compared to other samples, this sample also has the lowest Rp (polarization resistance) , Rp=233.57 (ohm.cm2 ) and the highest icorr (corrosion current) is icorr=3.46E-5 (μA/cm2 ) compared to other tested samples. Decreasing the current density from 0.4 to 0.3 amps caused the non-uniform distribution of nanoparticles and the crystal size in this coating and finally increased the corrosion current density in the sample. According to the results, it was observed that sample 9 (pulse reverse current coating) has better anti-corrosion performance than other samples, RP=4933.1 (ohm.cm2 ). Vickers hardness test was used to check the mechanical properties of the coatings and the results indicated that the hardness of the samples in the PRC plating current is higher than that of the PC plating current.

In this research, the effect of the organic substance N-N-diethylhydroxylamine (DEHA) along with multi layered graphene oxide (MLGO) in zinc-rich coating as a corrosion inhibitor on reducing the cathodic disbonding and increasing the corrosion resistance of steel substrates was investigated. For this purpose, paints with different weight percentages of DEHA and MLGO were made and applied on metal substrates. In order to investigate the adsorption of DEHA inhibitor on MLGO nanosheets and create interaction with it, the combination of N-Ndiethylhydroxylamine in a ratio of 2:1 with MLGO was investigated using FT-IR, TGA and SEM-EDX analysis. The inhibitory effect of DEHA in the coating was investigated by salt fog test and pull-off adhesion and cathodic disbondment and electrochemical impedance analysis. The results showed that by increasing the weight percentage of DHEA inhibitor compared to MLGO from 0.5 to 2% in the coating structure, the amount of cathodic disbonding decreased and the corrosion resistance increased significantly.

Magnesium and its alloys are very suitable for making implants in physiological environments such as the human body from the point of view of being biodegradable, and they also have a hardness close to the bone. In addition, the characteristics of magnesium include lightweight, high strength, and good biocompatibility, which has created a tremendous change in the field of medicine for the new generation of biomaterials. However, magnesium alloys are associated with high degradation due to the release of hydrogen gas and the improvement of the surrounding tissues. Magnesium implants lose their mechanical integrity during the healing period before the bone heals due to the high degradation process. Various methods and techniques have been proposed to control the amount of magnesium degradation to acceptable levels. This article discusses an overview of the types of conversion coatings, effective methods to increase the quality of these coatings, and the factors affecting the performance of conversion coatings in improving the corrosion resistance of magnesium alloys. Among the different approaches, chemical conversion coatings are the most simple and cost-effective method, which even can remove the weak points of components with complex designs such as implants and stents. The conversion coatings are uniform and very sticky, and the expected characteristics of the coating can be obtained easily by changing the temperature, pH of the bath, and other compelling features. In this research, the types of conversion coatings and the strengths and weaknesses of each of these coatings have been investigated.

The scanning Kelvin probe (SKP) is a non-destructive and non-contact method for surface inspection, which is widely used in evaluating the performance of corrosion inhibitors, investigating the mechanism of inhibition, determining the optimal concentration, and evaluating the effectiveness of inhibitors in different environments. This method provides information about the electrochemical behavior of the surface based on the measurement of the contact potential difference (CPD) between the sample surface and the reference electrode. A more comprehensive understanding of the corrosion process can be achieved by using the SKP method and comparing its results with electrochemical measurements such as electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP). In this research, the inhibition behavior of quaternary ammonium salts (QAS) against the corrosion of X65 carbon steel in the sour environment (H2S) at 60 °C was investigated using EIS and PDP tests, then the results were confirmed with the scanning Kelvin probe.

The purpose of this research was investigation the effectiveness of two organic inhibitors containing thiazole functional group for preventing corrosion based on the results of density function theory extracted from Gaussian 09W software and then comparing and verifying these results with the potentiodynamic polarization test results. The results showed that two corrosion inhibitors, Mercapto Benzo Thiazole and Aneurin, were film-forming and mixed type inhibitors and have the ability to prevent the corrosion of carbon steel in hydrochloric acid environment. The analysis of the results showed that the data obtained from the laboratory tests and the parameters extracted from the software were verified each other. Among these two inhibitors, MBT showed a higher inhibition percentage due to the presence of more and stronger heteroatoms and a higher tendency to donate electrons, so that the inhibition efficiency of 200 ppm of this inhibitor at 25 °C was reported 87%.

In this study, a synthesize hybrid nanocarrier by co-precipitation method consisting of double-layer hydroxide (LDH) and multi-walled carbon nanotubes (MWCNT) was used as a nanocarrier containing corrosion inhibitor in order to enhance the corrosion protection performance of applied epoxy coating on St12 substrate in 3.5 wt.% NaCl environment. Also, by adding sodium triphosphate (TSP) nanoparticles as a corrosion inhibitor to the synthesized hybrid nanoparticles, a smart anti-corrosion coating was made, which confirmed the correctness of the synthesis of MgAl-LDH/OMWCNT hybrid nanoparticles and the correction of loading of the TSP inhibitor molecule in the MgAL-LDH /OMWCNT structure by characterization tests such as XRD, Raman and FTIR and the corrosion inhibition mechanism was carried out using EIS, polarization and FE-SEM/EDS analyses. The polarization results showed the 20% reduction of corrosion current density. In the following, the anti-corrosion properties of the epoxy composite coating were investigated by EIS analysis. The results showed the active inhibition of the TSP-LDH/OMWCNT/EP coating in the scratch areas, in the other word an enhancement of Rct, from 65.97 k.cm2 for pure EP sample to 94.87 k.cm2 for TSP-LDH/OMWCNT/EP indicated the reflection of improvement self-healing behavior of the system. Moreover, the results of pull-off adhesion and cathodic delamination tests demonstrated the durability of the anti-corrosion properties of the coated samples with LDH/OMWCNT and TSP-LDH/OMWCNT nanoparticles due to better compatibility with the epoxy, which led to a decrease in adhesion loss and a 36% decline in the diameter of cathodic delamination to 36% and so it indicated the improvement in the corrosion resistance of epoxy coating.