Iranian Journal of Oil and Gas Science and Technology

Abstract The enormous demands for metal implant have given rise to a search for cheap material with good bio-tolerability and resistance to corrosion. Although stainless steel has these properties and is widely used for this purpose, its long term application is still a concern. The corrosion resistance of stainless steel depends on the passive layer. Herein, chemical surface treatment, including passivation, electropolishing, and acid cleaning is used for improving the corrosion-resistance property of AISI 316L and 304L. Cyclic polarization, electrochemical impedance spectroscopy, and EDX analysis were used to investigate the properties obtained thereby. Finally, the corrosion resistance of the untreated and modified specimens was compared. The results show that the corrosion behavior of the passivated and electropolished specimens is improved.

Abstract This paper presents a new multi-sensor data fusion method based on the combination of wavelet transform (WT) and extended Kalman filter (EKF). Input data are first filtered by a wavelet transform via Daubechies wavelet “db4” functions and the filtered data are then fused based on variance weights in terms of minimum mean square error. The fused data are finally treated by extended Kalman filter for the final state estimation. The recent data are recursively utilized to apply wavelet transform and extract the variance of the updated data, which makes it suitable to be applied to both static and dynamic systems corrupted by noisy environments. The method has suitable performance in state estimation in comparison with the other alternative algorithms. A three-tank benchmark system has been adopted to comparatively demonstrate the performance merits of the method compared to a known algorithm in terms of efficiently satisfying signal-tonoise (SNR) and minimum square error (MSE) criteria.

Abstract The influence of increasing the SiO2/K2O molar ratio on the electrochemical action of a waterborne potassium silicate zinc-rich coating was investigated by means of electrochemical impedance spectroscopy (EIS) and corrosion potential (Ecorr) measurements. The EIS results showed that increasing the SiO2/K2O molar ratio in the range of 3.135 to 5 by the addition of nano-SiO2 to the resins improved the resistance of coatings; however, higher molar ratios showed an adverse effect. Moreover, the alkali silicate binder of the sample with a SiO2/K2O molar ratio of 5 was improved by adding 5, 10, and 15 wt.% of acrylic resin and acrylic/styrene copolymer to potassium silicate resin. These formulated coatings were sprayed over carbon steel plates and the adhesion and morphology of these primers were evaluated by pull-off, cross cut, and scanning electron microscopy tests. Electrochemical measurements showed that the sample with a SiO2/K2O molar ratio of 5 had better corrosion properties than the other samples. Adhesion and SEM tests also showed that B1 and C2 with respectively 5 and 10% acrylic derivatives had less holes, cracks, and better adhesive properties.