مجله علوم و مهندسی خوردگی
سال پنجم شماره 3 (پیاپی 17، پاییز 1394)

The inhibition behavior of 1H-benzotriazole on corrosion of mild steel and Aluminum alloy 1050 in single and couple modes was investigated in sea water by immersion, Tafel polarization and electrochemical impedance spectrometry methods. The results indicated that an increase in inhibitor concentration cause to enhance in inhibition efficiency for both MS and AA1050 in single mode. In this case, the use of 0.01 M BTA caused to 50 and 70 percent reduction in corrosion rate of mild steel and AA 1050, respectively. BTA adsorbed on both MS and AA1050 surfaces physically according to the Langmuir adsorption isotherm. BTA was adsorbed on mild steel surface chemically when mild steel coupled to AA1050 which in turn caused the corrosion rate of mild steel to reduce more than 95 percent with respect to reference sample.

In the present work, the application of 8-hydroxyquinoline (8-HQ) as a ferric ion sensitive indicator, in epoxypolyamine coating was investigated. Having turn-on mechanism and showing no prematurely fluorescence when mixed with the coating precursors make 8HQ useful for detecting undercoating corrosion of St-37 which is covered by epoxy coating. The effect of different concentrations of 8HQ(0.05,0.1,0.5, w.t%) in epoxy coating, on corrosion detection, optical, electrochemical and adhesion properties of applied coating were studied respectively by fluorescence microscopy, UV- Visible spectroscopy, electrochemical impedance spectroscopy and Pull-off methods. In the process, the sample with 0.1w.t% of 8HQ not only, showed acceptable corrosion detection performance, but also was good in optical, electrochemical and adhesion properties.

The electrochemical behavior of specified aluminium alloys, due to their usage in cathodic protection systems and batteries such as aluminium batteries, has always been considered. The aim of this study was to design an aluminium alloy for use as an anode in aluminium batteries with saline electrolytes. Aluminium alloy with Al-Mg-Sn-Ga structure was made by stir casting technique and corrosion behavior of this alloy was evaluated using different techniques. Microstructural studies were made using optical microscopy and scanning electron microscopy. It is known that the tin particles may be either in solid solution or may be segregated as second phase particles or intermetallic compounds in the alloy and cause the active dissolution of alloy exhibiting anodic behavior. The results of immersion, open circuit and closed circuit potentials, hydrogen evolution, polarization, electrochemical impedance spectroscopy and anodic efficiency tests showed that in chloride containing mediums, alloy had an anodic behavior.

Nanocomposite coating was applied on commercial pure titanium using plasma electrolytic oxidation (PEO) process in suspension containing sodium phosphate and alumina nanopowder with environmentally friendly penicillin G benzathine inhibitor. This process was conducted by direct current and at constant current density. Effect of penicillin concentration on coating growth, absorption of alumina nanoparticles (suspended in the electrolyte), morphology, corrosion behavior of coating by energy dispersive X-ray spectroscopy, scanning electron microscopy and cyclic potentiodynamic polarization test was investigated. The results revealed that breakdown voltage in the presence of penicillin is increased up to 8%. The percentage of porosity in coating surface increased to 40% with increasing concentrations of penicillin. Thickness of coating in electrolytic containing penicillin has been halved. Concentration of 1.5 gr/Lit penicillin as an optimum concentration leads to improve the corrosion behavior of these samples relative to treated samples with no additives.

Nowadays, good adhesion and healing abilities of self healing coatings cause to these coatings are one of the most conventional methods to repair and corrosion protection of materials. The hybrid self healing coating plays an important role in corrosion protection of materials against kinds of all corrosion. In this paper, Titania- Benzotriazole nanostructured coating applied by sol-gel process with using immersion methods on Aluminum alloys 7075. Then structure and morphology and also corrosion behavior of coatings are investigated by using field emission scanning electron microscopy (FE-SEM) and electrochemical impedance analyses, respectively. The results represent the creation of a homogeneous, uniform and crack free coating on Al 7075, cause to improved corrosion resistance in 3.5% NaCl solution.

These days, most of the marine structures which are used in industry, are made of steel. The most typical way to prevention of corrosion is use of organic coatings. In this research a epoxy coatings and styrene butadiene rubber(SBR) which contains 0, 2, 4 and 6 % of nanoparticles of Copper oxide (CuO) coated on surface steel plates. The surface morphology properties of these coatings were characterized by scanning electron microscopy. The effect of incorporating percent nanoparticles on the corrosion resistance of SBR and epoxy-coated steel was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. Abrasion and adhesion test was used to evaluate strength coatings. The electrochemical monitoring of the coated steel over 35 days of immersion in both 3.5 wt.% NaCl solutions suggested showed that the coating with 4% nanoparticles of Copper oxide have better corrosion resistance. It was obviously indicated that the existence of nanoparticles of Copper oxide can improve the resistance properties of the coatings at an optimize content of zinc which was 4% in this system. The coatings contains 6% of nanoparticles of Copper oxide had the worse result was worse than the other samples.

The corrosion behaviors of electrodeposited Fe-Ni-Cr amorphous- nanocrystalline coatings were the aim of this study. For this regards, the electrodeposition process was done at different current density and the annealing process was also done at 250ºC for different periods of time. The produced samples were characterized using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The corrosion behaviors of coatings were also examined in NaCl 3.5% electrolyte by potansiostate analysis. The results showed that, the full amorphous Fe-Ni-Cr coating can successfully produced by electrodeposition processing from chloride bath at current density higher than 30 A/dm2. The produced as-deposited amorphous coatings exhibit good corrosion resistance with the corrosion potential and current density in the range of 350-400 mV and 0.2-0.5μA/cm2, respectively. By annealing the produced coating, the amorphous phase crystallized to nanocrystalline Fe and FeNi phases. The corrosion resistance of coatings decreases by crystallization of amorphous phase.