Hydrothermal Corrosion of Double Layer Glass/Ceramic Coatings Obtained from Preceramic Polymers

Polysilazane-based double layer composite coatings consisting of a polymer-derived ceramic (PDC) bond-coat and a PDC top-coat that contains ceramic passive and glass fillers were developed. To investigate the environmental protection ability of the prepared coatings, quasi-dynamic corrosion tests under hydrothermal conditions were conducted at 200 °C for 48–192 h. The tested PDC coatings exhibited significant mass loss of up to 2.25 mg/cm2 after 192 h of corrosion tests, which was attributed to the leaching of elements from the PDC coatings to the corrosion medium. Analysis of corrosion solutions by inductively coupled plasma optical emission spectrometry (ICP-OES) confirmed the presence of Ba, Al, Si, Y, Zr, and Cr, the main component of the steel substrate, in the corrosion medium. Scanning electron microscopy (SEM) of the corroded surfaces revealed randomly distributed globular crystallites approximately 3.5 µm in diameter. Energy-dispersive X-ray spectroscopy (EDXS) of the precipitates showed the presence of Ba, Al, Si, and O. The predominant phases detected after corrosion tests by X-ray powder diffraction analysis (XRD) were monoclinic and cubic ZrO2, originating from the used passive fillers. In addition, the crystalline phase of BaAl2Si2O8 was also identified, which is in accordance with the results of EDXS analysis of the precipitates formed on the coating surface.

The Effect of the Corrosion Medium on Silane Coatings Deposited on Titanium Grade 2 and Titanium Alloy Ti13Nb13Zr

The present paper focuses on the fabrication of coatings based on vinyltrimethoxysilane and the influence of various corrosion media on the coatings produced. Coatings were deposited on two substrate materials, namely, titanium Grade 2 and titanium alloy Ti13Nb13Zr, by immersion in a solution containing vinyltrimethoxysilane, anhydrous ethyl alcohol, acetic acid and distilled water. The obtained coatings were characterized in terms of surface morphology, adhesion to the substrate and corrosion resistance. As corrosion solutions, four different simulated physiological fluids, which differed in the contents of individual ions, and a 1 mol dm−3 NaBr solution were used. The chloride ions contained in the simulated physiological fluids did not lead to pitting corrosion of titanium Grade 2 and titanium alloy Ti13Nb13Zr. This investigation shows that titanium undergoes pitting corrosion in a bromide ion medium. It is demonstrated that the investigated coatings slow down corrosion processes in all corrosion media examined.

Effect of Service Environmental Parameters on Electrochemical Corrosion Behavior of L80 Casing Steel

The corrosion behavior of L80 casing steel was studied in a simulating annulus environment using the electrochemical measurement method, immersion test, and tensile test under a high-temperature and high-pressure H2S/CO2 environment. The partial pressure of CO2 (PCO2), the partial pressure of H2S (PH2S), water content, and preloading stress remarkably affected the corrosion behavior of L80 steel. The influence of PCO2 on stress corrosion cracking (SCC) susceptibility has an inflection point of approximately 1.1 MPa. The SCC susceptibility reaches the maximum when the PCO2 is about 1.1 MPa. The SCC susceptibility has a positive correlation to PH2S and water content. The higher water content of the corrosion medium can increase the electrical conductivity of the corrosion medium and promote the corrosion of L80 steel, which can improve the diffusion of hydrogen into steel and promote the SCC of L80 steel. Preloading stress can promote local corrosion, thereby promoting SCC of steel under stress. The dislocation emergence point caused by preloading stress can accelerate the diffusion of hydrogen into steel and increase SCC susceptibility.

Protective Efficiency of ZrO2/Chitosan “Sandwich” Coatings on Galvanized Low-Carbon Steel

Enhanced corrosion efficiency of low-carbon steel was achieved by newly developed hybrid multilayers, composed of low-carbon steel coated with an electrodeposited zinc sublayer (1 µm), a chitosan (CS) middle layer and ZrO2 coating by the sol–gel method (top-layer). The middle chitosan layer was obtained by dipping galvanized steel substrate in 3% tartatic acid water solution of medium molecular-weight chitosan, composed of β-(1–4)-linked D-glucosamine and N-acetyl-D-glucosamine with a deacetylation degree of about 75–85% (CS). The substrates were dipped into CS solution and withdrawn at a rate of 30 mm/min. One part of the samples with the CS layer was dried at room temperature for 2 weeks, and another part at 100 °C for 1 h, respectively. After CS deposition treatment, the substrates were dipped into an isopropanol sol of zirconium butoxide with small quantity of polyethylene glycol (PEG400). The dipping-drying cycles of the ZrO2 coatings were repeated three times. After the third cycle, the final structures were treated at 180 °C. The samples were denoted as T25, which consists of the CS middle layer, and dried at RT and T100 with the CS middle layer treated at 100 °C, respectively. The samples were characterized by means of differential thermal analysis (DTA-TG), XRD analyses, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Hydrophobicity properties were evaluated by measuring the contact angle with a ramé-hart automated goniometer. Two electrochemical tests—potentiodynamic polarization technique (PD) and electrochemical impedance spectroscopy (EIS)—have been used to determine the corrosion resistance and protective ability of the coatings in a 5% NaCl solution. The results obtained by both methods revealed that the applied “sandwich” multilayer systems demonstrate sacrificial character and will hopefully protect the steel substrate in corrosion medium containing chloride ions as corrosion activators. The newly obtained hybrid multilayer coating systems have dense structure and a hydrophobic nature. They demonstrated positive effects on the corrosion behavior at conditions of external polarization independent of their various characteristics: morphology, grain sizes, surface roughness and contact angle. They extend the service life of galvanized steel in a chloride-containing corrosion medium due to their amorphous structure, hydrophobic surface and the combination of the positive features of both the chitosan middle layer and the zirconia top layer.

Analysis of Corrosion Breakdown Rate in Low Carbon Steel with Aluminum Coating

This study aims to analyze the corrosion penetration rate of low carbon steel with aluminium coating. The method used is the potentiodynamic method to determine the value of the corrosion rate. The corrosion medium used was HCl. The aluminium used is aluminium frame waste powder. The coating process is by dipping low carbon steel pipes into aluminium frame waste that had been liquefied in the Hot Dip Galvanizing (HDG) method of 700oC and immersion time of 45 seconds. The results of this study show that low carbon steel which has been coated with aluminum frame waste powder has a high corrosion rate which is proven to have a corrosion rate of 18,1808 mm/year. So that the corrosion rate is at an unacceptable level.

EFFECTS OF TEMPERATURE ON MILD STEEL GRADIENT-DISTRIBUTED WBE IMMERSED IN 3.5 wt.% NaCl SOLUTION

To study the corrosion behavior of carbon steel in seawater at different temperatures, a novel electrochemical method called gradient-distributed wire beam electrode technique with high temporal and spatial resolution has been employed. This new wire beam electrode was prepared by three kinds of carbon steel with different carbon contents so that it can evaluate three materials simultaneously in the same corrosion medium (3.5[Formula: see text]wt.% NaCl solution) and improve the accuracy of tests results. After the gradient-distributed wire beam electrode soaked in 3.5[Formula: see text]wt.% NaCl solution for 8[Formula: see text]h, compared with measured at room temperature, the corrosion rate was accelerated greatly and polarity reversal of potential-current was also observed.

SINTESIS GREEN INHIBITOR EKSTRAK DAUN TREMBESI (Samanea saman (Jacq.) Merr) SEBAGAI PEREDUKSI LAJU KOROSI LOGAM BAJA KARBON

Extract of trembesi leafs consist tannins compound that can reducing corrosion rate. This studey was to examine the efficiency of trembesi leaf extract as a inhibitors of corrosion rate. In this study, carbon steel metal was used as an immersion object in 10% HCl solution as a corrosion medium. Trembesi leaf extract were added in the corrosive medium with variations in volumes of 3, 6, 9, 12 mL with carbon steel immersion for 14 days. Corrosion rate was calculated using the weight loss method. The results shows, the lowest corrosion rate was obtained in the addition of 9 mL inhibitor concentration of 0.008989 cm/year and the highest corrosion rate was without the addition of an inhibitor of 0.011669 cm/year. The highest inhibitor efficiency value was 22.97% with the addition of 9 mL.

Microstructure and Corrosion Behavior of Cold-Sprayed Zn-Al Composite Coating

A Zn–Al composite coating was successfully deposited on Q235 steel by cold spray technology for the corrosion protection in the marine atmosphere. The microstructure and corrosion behavior of the prepared coating was studied byScanning Electron Microscope (SEM), X-ray Diffraction (XRD), salt spray test and electrochemical experiments. A 2400-h neutral salt spray corrosion test (with a corrosion medium of 3.5% sodium chloride solution) showed that the prepared cold-sprayed Zn-Al composite coating has excellent anti-corrosion properties. Based on the microstructure evolution and corrosion products analysis, droplets’ flow-driven ‘synergistic corrosion effect’ was proposed to explain the co-corrosion behavior of Zn and Al particles in the composite coating.