SCIENCE AND ENGINEERING CORROSION
Year:2016 | Volume:6 | Issue:10 (20)|Papers Count:7

In this paper, the effect of cerium chloride with solution features of immersion time=15 minutes, concentration of cerium=5 gr/lit, pH=5.5 at room temprature on the anti-corrosion behaviour of zirconium- coated steel in optimized condition with immersion time = 90 seconds, 0.01 molar H2ZrF6 and pH=4 was investigated. The results of EIS test showed that the corrosion resistance of steel without coating, with zirconium conversion coating and with zirconium-cerium conversion coating was 520, 1150 and 2400 W/cm2 respectively. DC polarization test showed that the corrosion current density decreasd from 8.2 to 1.6 mA/cm2. The addition of 200 ppm nickel sulphate to the cerium conversion solution increased the corrosion resistance of Zr-modified steel to 3300 W/cm2.

Conversion Coatings Based on Rare Earth Elements From an Environmental Standpoint are a Good Alternative for Chromate Conversion Coatings. There are a lot of Cracks in the Structure of These Coatings and Because of This the Main Foible of These Coatings is Undesirable Anti-Corrosion Properties. Different Additives Have Been Used in the Formulation of These Coatings to Improve the Properties. In This Study, at First the Formulation of an Eco-Friendly Cerium Based Conversion Coating is Optimized. In the Next Step, the Effect of Presence of Polyvinyl Alcohol (PVA) as an Eco-Friendly Additive on the Anti- Corrosion and Morphological Properties of the Coating on a Steel Substrate is Investigated. DC Polarization, SEM, EDS, XRD and Contact Angle Tests Have Been Utilized to Analyze the Samples. The Results Show that the Presence of PVA in the Coating Formulation Reduces the Number of Cracks in the Structure of the Coating and Leads to Formation of a Coherent and Corrosion Resistant Coating. Consequently, it Can be Said that Polyvinyl Alcohol (PVA) Acts as an Inhibitor on the Steel Substrate and By Means of Creating Complexes in the Anodic and Cathodic Areas may Improve the Anti-Corrosion Properties of the Cerium Based Conversion Coating. Based on the Results, the Lowest Corrosion Rate is Related to the Conversion Coating Containing the Maximum Concentration of Poly Vinyl Alcohol.

In this study the corrosion performance of epoxy and SiAlON - epoxy nanocomposite powder coatings were investigated. Given that ball mill process has so far received little attention, in this study, nanocomposite powder produced by this method are discussed. Corrosion properties of coatings were assessed by immersion and electrochemical impedance spectroscopy tests in 3.5% NaCl solution. The results show that adding 10 wt% SiAlON nanoparticles markedly increases corrosion resistance of epoxy coatings. Higher corrosion resistance of nanocomposite coatings can be attributed to the barrier properties of SiAlON nanoparticles. According to these results, it can be concluded that epoxy powder coating containing 10 wt% SiAlON nanoparticle, can be widely used as coating pipelines in oil, gas and petrochemical industries.

In This Article the Influence of Myrtus on the Corrosion of Aluminum (2SR) in 3.5 wt. % Sodium Chloride Was Studied by Means of Electrochemical Impedance Spectroscopy and Polarization and Surface Analysis Methods. It Was Shown that Addition of the Green Corrosion Inhibitor in Corrosive Media Reduced the Corrosion Rate. Increase in the Concentration of Green Corrosion Inhibitor Lead to an Increase in Inhibition Efficiency Reaching to a Maximum at 800 ppm. The Mechanism of Green Corrosion Inhibitor That was Shown by Polarization Test is Mixed of Anodic and Cathodic. The Analyzing Data That Extracted From Surface Analyzing Show That Pitting Corrosion Happened in Salty Media and Green Corrosion Inhibitor Can Prevent the Pitting Corrosion as Well.

In this work, polysulfide and nano cerium oxide were added to epoxy in order to modify the toughness and corrosion resistance properties of epoxy resin. For this purpose, polysulfide in different weight percentages (5-25 wt%) was mixed with epoxy resin. The physical properties and corrosion resistance of the coated samples were evaluated by pull off adhesion tests, cupping, electrochemical impedance and salt spray. Results showed that the addition of 10 wt% polysulfide to epoxy, led to increasing corrosion resistance and toughness. Also, by adding different weight ratio of nano size CeO2 (0.5-6 wt%) to the composition of epoxy/polysulfide resin, anticorrosion and adhesion characteristics of the resultant coatings improved. The results showed that the presence of low concentrations of nano CeO2 (about 1 wt%) led to the best anti-corrosion and adhesion properties. Results of FESEM test showed that the dispersion of nano CeO2 in the matrix was completely uniform.

In This Article, Pure Zn and Zn-12%Ni Coatings Were First Applied by Electroplating Using an Alkaline Bath on the High Tensile Strength Cr - Si Spring Steels and Then the Effect of Electroless Plating of a Nickel Interlayer on Corrosion Behavior of Those Coatings Was Assessed and Compared Due to Tafel Plot and Electrochemical Impedance Spectroscopy (EIS). Polarization Test Results Shows That Alloying Zn With Nickel Shifts the Corrosion Potential Towards More Noble Values and Reduces the Corrosion Current. The Presence of the Nickel Interlayer Alters the Corrosion Potential of the Pure Zn Coating from -1044 mV to -1188 mV and the Corrosion Current from 43.1 mA to 119.4 mA. Besides, the EIS Results Indicate that the Coating’s Polarization Resistance Decreases Significantly as a Result of the Nickel Interlayer. The Values Reduce 64% and 77% for Pure Zn and Zn-12%Ni, Respectively.

Trivalent Chromium Composite Coatings Have Been a Proper Replacement for Hard Chromium Coatings Including Chromium VI due to Their Environmental and Mechanical Properties .in this Study the Process of Pulsed Current Electroplating has Been Utilized in Order to Produce Chromium Coating from Chromium III bath to Apply on Steel Substrate. Current Density, Plating Time and Surface Roughness Were Considered as a Variable Conditions. For This Purpose and in Order to Apply a Coating in Optimum Conditions of Plating, With the Aim of Increasing The Thickness and Uniformity of Coating, Taguchi Experimental Design Was Used. By Addition of Various Amounts of SiC 15, 5 gr/li to Containing Bath in Optimum Conditions of Plating the Corrosion Behavior of Chromium Coating and Composite Coating with 5 and 15 gr/lit of SiC was Studied by Impedance a Tafel tests .Base on The Results, Samples With Pulse Current of 10 amp/dm2, Roughness of 325 Micrometer and Duration of 60 Minutes Have Been Considered the Optimized Samples Which Has the Thickest Coating of 40 Microns .Further More in Order to Study the Corrosion of the Coating Impedance and Tafel test Have Been Carried Out .Base on the Electrochemical Parameters Obtained From Tafel and Impedance, Corrosion Rate of Composite Coating in Relation With Chromium Coating Without SiC Has Increased. With the Increasing SiC in Composite Coating from 5 to 15 The Corrosion Rate Has Increased.