T. Fedotova

Electrochemical studies of mild steel corrosion inhibition in sulfuric acid chloride by aniline

The corrosion behavior of mild steel in dilute hydrochloric acid under the inhibiting action of various concentrations of aniline was studied using the weight loss and linear polarization resistance technique. The efficiency of the inhibitor increased with the increase in the inhibitor concentration. The results obtained reveal that aniline performed effectively as a corrosion inhibitor. The adsorption mechanism indicates mixed molecular interaction from values of Gibbs free energy. The values of the inhibition efficiency calculated from the two techniques are in reasonably good agreement. The adsorption of the inhibiting compound was found to obey Langmuir, Frumkin and Freudlich adsorption isotherms. The mechanism of inhibition was discussed in the light of the chemical structure of the inhibiting compound and their adsorption on steel surfaces in relation to the potentiodynamic parameters.

Electrochemical Studies on the Corrosion Behaviour of Laser Alloyed Zn-Sn Coatings on UNS G10150 Steel in 1M HCl Solution

Surface deterioration by corrosion is one of the complications associated with ageing facilities and components especially under some service environments. This study was designed to investigate the enhancement in the corrosion and hardness properties of UNS G10150 steel laser alloyed with three different premixed compositions of Zn-Sn binary powders using a 4.4 KW continuous wave (CW) Rofin Sinar Nd:YAG laser processing system. The steel alloyed samples were cut to corrosion coupons, immersed in hydrochloric acid (1M HCl) solution at 30 °C using an electrochemical technique and investigated for their corrosion behaviour. The morphologies and microstructures of the developed coatings and uncoated samples were characterized by an Optic Nikon Optical microscope (OPM) and a scanning electron microscope (SEM/EDS). Moreover, a X-ray diffractometer (XRD) was used to identify the phases present. An improvement of 2.5-times the hardness of the steel substrate was achieved in A1(0.8) which may be attributed to the fine microstructure, dislocations and the high degree of saturation of solid solution brought by the high scanning speed. At a scanning speed of 0.8 m/min, sample A1 exhibited the highest polarization resistance Rp (3163000 O.cm2), lowest corrosion current density icorr (7.95X10-8A/cm2), with a lowest corrosion rate Cr (0.000924 mm/year) in 1M HCl solution. The polarization resistance Rp (3163000 O.cm2) is 392,281-times the polarization of the UNS G10150 steel substrate with a 99.9994 % reduction in the corrosion rate.

Nd: YAG laser treatment of aluminium —C TiB2 coated: Optimization of corrosion properties

As the reports in the literature regarding corrosion performance of Al/TiB2 MMC are rather contradictory, the optimization of laser surface alloying parameters for these composite coatings seems to be necessary. The characterization of the MMC was carried out by optical microscopy (OM), scanning electron microscopy (SEM/EDS) and x-ray diffraction (XRD). Partial melting of the alloying powder occurred and the chemical reactions with the a-Al in the matrix led to the formation of AlTi and AlB2 phases. Eutectics of TiB2/Al and TiB2/Ti were observed. The results of the tests indicate that TiB2 reinforcement does not give significant increase in microhardness of aluminium. The corrosion resistance of a single laser trackline MMC in a 3.65 % NaCl solution was improved, especially for the sample produced at high scan speed, with the lowest volume fraction of TiB2 particles.