مجله علوم و مهندسی خوردگی
سال سیزدهم شماره 2 (پیاپی 48، تابستان 1402)

In order to improve the corrosion resistance of polymer (ABS) components, electroplated nickel-chromium coatings and solutions were introduced to increase resistance to corrosion and remove surface micro-defects in chrome cathodic arc coatings during the coating process. Six solutions were examined: micro-etching with argon plasma, ion bombardment, increasing coating thickness, creating chromium nitride and titanium nitride multilayers, creating coatings with gradient bias voltage, and removing chromium layers during the plating process. Combination coatings of Cr-CrN-Cr and Ti-TiN-Cr with multilayer structures were used on electroplated polymer substrates for coating car handles. Surface treatments were applied in the common sublayer-coating interface. The corrosion behavior of the coatings was investigated using the Copper Accelerated Salt Spray (CASS) test method. The results of CASS showed that surface treatment improves the corrosion resistance of coatings by 50-60%. By eliminating droplets and inclusions on the surface using surface treatments and changing the columnar structure of the coating with bias voltage changes prevents the formation and growth of diffusion paths throughout the defects and prevents the formation of corrosion cells. Furthermore, by removing the electroplated chromium layer and applying coatings onto nickel electroplating, corrosion resistance was improved by up to 80%, providing a hopeful solution for improving the corrosion resistance of coated parts.

Chromium coated zirconium alloys are one of the promising options for accident resistant fuel cladding (ATF) tubes for light water reactors (LWRs). In this study, the oxidation behavior of the chromium coating deposited by the physical vapor coating method on the zirconium substrate was investigated. The scanning electron microscope image of the cross-section of the samples and the atomic force microscope image of the sample surface show that a chromium layer with an approximate thickness of 20 nm and a lower surface roughness of 680 nm is formed on the surface. The results of EIS and PDP spectroscopic tests, in the aqueous environment of 3.5 wt% NaCl, show that the corrosion potential and current from -0.371 V and 5.85 ×10-8 A for the uncoated sample to -0.354 V And A has changed 0.65×10-8 , which indicates the improvement of oxidation resistance of the sample coated with Cr.

The main chemical treatment of the cooling network is done with two chemicals; anti-corrosion and anti-fouling. These two chemicals act as complements. The nature of the make-up water entering the cooling network of Mahabad Petrochemical Complex is sedimentary. In the sedimentary waters, according to LSI, scaling control is more important than corrosion. Therefore, even if the uniform corrosion rate increases up to 1 MPY, its economically and technically better than blocking and scaling damage such as pitting corrosion. The Anti-fouling agent plays a major role in controlling scale. This substance is a combination of different polymers that can control the scale in the circulating water of the cooling system and prevent the formation of scale with the mechanism of dispersing sediment-causing salts and prevent the formation of corrosion under the sediment. The type of polymer used and its concentration are very important in the effectiveness of the antifouling agent. Usually, in order to avoid specifying the formula of the substance, the supply companies refuse to provide the type of polymer used and do not provide measurable laboratory parameters to ensure the effectiveness of the injection of the substance, so the effectiveness of the substance used is determined in test run. to achieve this purpose, two groups of chemicals, including anti-corrosion and anti-fouling materials, were field tested to determine the actual corrosion rate, LSI, RSI coefficients, the appearance of the coupons installed on the corrosion rack, and the actual consumption.

The formation of various scales in industrial equipment has always caused many problems for industries such as oil and gas. One of the efficient methods to deal with and remove these scales is the acid pickling method. Since the acids used in acid pickling processes often cause corrosion to the metal of the substrate, it is very important to use a solution with a low corrosion rate as a substitute for these acids to remove deposits from the equipment. One of the effective scale removal solutions with high scale removal power and low corrosion rate is Mitreh Sard with code MDA0102. In this research, an attempt was made to investigate the corrosiveness of this solution compared to hydrochloric acid solution for C1010 steel and Titanium with the help of electrochemical impedance spectroscopy and potentiodynamic polarization tests. The results of the tests showed that the corrosion rate of the MitrehSard solution is lower than that of the hydrochloric acid solution in all the studied concentrations.

The quality of low-pressure condensate steam, which is one of the important process fluids in the gas refining industry, in addition to its effect on the continuity and quality of refinery products, can be effective on the health and mechanical integrity of equipment and piping systems. The presence of destructive elements such as oxygen and carbon dioxide in the consumed steam and selected steam leads to severe corrosion in the piping system and equipment made of carbon steel. In this research, the causes of corrosion of the destroyed pipe with API 5L Gr.B material carrying low-pressure gas condensate steam related to one of the process units in one of Iran gas refineries have been evaluated. For this purpose, while reviewing technical documents and various characterization techniques such as stereography, spark emission spectrometry analysis, optical microscope, scanning electron microscope, analysis of corrosion products by X-ray fluorescence and measurement of dissolved oxygen in the fluid was carried out. The appearance of the created corrosion is similar to the corrosion caused by oxygen. Also, the results of the analysis of the remaining corrosion products on the inner surface of the pipe and inside the created holes showed the presence of iron oxide. Therefore, it was finally determined that the pipe in question suffered from corrosion caused by oxygen.

In this paper, organic/inorganic hybrid pigment based on sodium lignosulfonate and zinc acetate was synthesized for reducing the corrosion rate of St12 steel immersed in 3.5 wt.% NaCl solution. To evaluate the anti-corrosion protection performance of steel substrate immersed in solution in the presence and absence of synthesized pigment, electrochemical impedance spectroscopy, potentiodynamic polarization and open circuit potential tests were performed. Scanning electron microscope equipped with energy dispersive spectroscopy and X-ray diffraction tests were also used to evaluate the inhibition mechanism of pigment. The results of the electrochemical impedance spectroscopy test showed that the charge transfer resistance of steel sample increased from 2958 Ω.cm2 to 7500 Ω.cm2 after 120 h of immersion in the saline solution with pigment. The formation of an inhibitive film consisting of zinc and lignosulfonate complexes on the surface of the steel substrate is the main reason for enhancing of the charge transfer resistance of the steel substrate in the presence of the synthesized pigment.