Corrosion Engineering,Science and Technology: The International Journal of Corrosion Processes and Corrosion Control

The alternating current (AC) has a strong influence on the corrosion of carbon steel Q235 in soil. AC corrosion^1-3 was investigated by morphology observation, weight loss analysis and electrochemical measurement. The results of morphology observation and weight loss analysis showed that AC increased the corrosion rate and the influence was weakened when a protective layer was built up. The electrochemical tests confirmed that in the presence of AC, the corrosion potential shifted toward the negative direction and the exchange current density increased.^4-9

Investigation of corrosion rate under the simultaneous effect of parameters is a new and important approach that makes our experimental media closer to real condition and offers more realistic results. In this study, the effect of some important marine factors including temperature, pH, velocity and salinity on the corrosion rate of SS 316 is considered synergistically using two by two graphical curves. Experiments are performed in turbulence condition, and each parameter is applied at three levels. The results of this research are compared with the achievements of a former synergistic study of parameters, which had calculated the contribution percentage and qualitative influence of marine factors in laminar condition. This research presents the critical points in the change of corrosion rate under the synergistic effect of parameters and compares the capability of factors in changing the rate of corrosion and studies their qualitative effect.

In this paper, the influence of the tin content on the corrosion behaviour of copper alloys was investigated. Three different bicomponent bronze alloys were exposed to a natural urban environment. The kinetic corrosion processes and the patina properties were monitored using the open circuit potential, electrochemical impedance spectroscopy and spectrocolorimetry. Results show that the bronze corrosion behaviour improves upon increasing the tin content. In addition, the mechanism of the patina formation is different for the three alloys.

Some 17 4PH propeller shafts showed severe localised corrosion after a long period of time in Ancona harbour. The shaft is concentrically mounted in an AISI 304 stern tube through two rubber bearings. Both 17 4PH and AISI 304 stainless steels were characterised by anodic polarisation in natural sea water, in order to obtain the necessary corrosion parameters for designing a suitable cathodic protection of the propeller system. The cathodic protection effectiveness was tested on a portion (about 1 m long) of this system. Two cathodic protection methods were tested: an impressed current cathodic protection at −0·3 V(SCE) and a galvanic cathodic protection. The tests were performed both in stagnant and in moving sea water and the results showed that these cathodic protection solutions were able to protect the propeller system; in particular some guidelines are suggested for both old and new ships.

In the present study, the influence of processing parameters of friction stir welding on the corrosion rate of the welded joints of aluminium SiC–Gr hybrid composites was investigated. The experimental results indicate that the corrosion resistance of the welded joints increases at high welding (traverse) speed and/or low values of rotational speed. These variations occur as a result of the changes in the joint microstructure, where fine grains are developed as a consequence of a relatively low heat input and fast cooling to room temperature by ambient air associated with low rotational speed and/or high welding speeds. The mixed electrode theory is used to explain these variations of the corrosion rate, where the area ratio of cathode/anode for the galvanic couple between the aluminium metal matrix and the reinforcement constituents becomes small for fine grains. Thus, the corrosion resistance of the welded joints is increased.

Electroplated nickel was chemically modified using an aminosilane coupling agent (as an alternative to chromate) in order to improve its corrosion performance. Infrared spectroscopy revealed that the silane bonded to the metal satisfactorily. The corrosion behaviour of a nickel electroplated steel workpiece was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy to optimise the silane deposition conditions. These data confirm that the most effective conditions are dipping in the silane coupling agent solution for 30 s and then curing at 100°C for 40 min.

This paper presents a discussion on assessing the potential impacts of climate change on the atmospheric corrosion rates of exposed steel structures. The effects on atmospheric corrosion due to changes in the environmental temperature, carbon dioxide, relative humidity, wind, rainfall and pollution are considered. The limitations and complexities of these assessments are discussed. To demonstrate the use and limitations of this science to evaluate effects related to climate change, a model developed in Australia to predict corrosion is combined with climate change models to project the change in the corrosion rates of steel components and protective zinc coatings in constructions. The method is applied to constructions located along the coastal areas of two Australian cities: Melbourne and Brisbane. These assessments are made using the A1FI scenario, the highest emission scenario defined by the Intergovernmental Panel on Climate Change, applied to nine general circulation models. The projected changes in corrosion rates were found to be an increase of ∼14% for both zinc and steel in Brisbane and a decrease of ∼14% for steel and 9% for zinc in Melbourne. It was also found that the uncertainties associated with the climate change models were small compared to those involved in modelling corrosion for engineering purposes.

This paper aimed at an experimental investigation of the comparative corrosion phenomenon in the reinforcing steel of repaired chloride contaminated self-compacting concrete (SCRC) and ordinary concrete (OC) patches. This research is a continuation of a previous study in which macrocell specimens were prepared with OC having different chloride contaminations simulating the actual patch repair in the construction field. Here, in this research, the same specimens were prepared with SCRC to investigate more deeply the macrocell phenomenon in SCRC, which received limited attention in the past. Four prismatic specimens with two sets of 5 and 3% chloride contaminated SCRC at the two ends were prepared respectively, and the middle portion of these specimens was cast after 24 h with uncontaminated SCRC simulating the actual patch repair in the field. After 1 year of experimental observations of corrosion potentials and corrosion rates, interesting and novel results were obtained in comparison with OC and SCRC specimens.

High temperature and high pressure immersion tests in an autoclave were employed to study the corrosion behaviour of X52 pipeline steel in aqueous solutions containing high concentrations of H₂S. The corrosion products generated were characterised using scanning electron microscope, energy dispersive spectroscopy and X-ray diffraction. It was seen that at a constant H₂S concentration of 22 g/l, the corrosion rate increased with increasing temperature up to 90°C, thereafter decreased at 120°C and slightly increased again at 140°C while the corrosion rate increased with H₂S concentration at a temperature of 90°C. When the temperature and H₂S concentration increased, the corrosion product converted from iron rich to sulphur rich products in the following sequence: mackinawite→troilite→pyrrhotite, where the microstructure and stability of the corrosion products had an important effect on the corrosion rate. The corrosion film was formed through the combination of the outward diffusion of Fe²⁺ ions and the inward diffusion of H₂S and HS⁻ species.

The corrosion behaviour of 316L stainless steel (316L ss) in aqueous solutions of ionic liquid 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]) with different contents of water was investigated by scanning electron microscopy (SEM), potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS). The results indicate that 316L in aqueous solutions of ionic liquid [EMIM][DEP] shows an obvious surface passivation, a broad passive region and low corrosion current densities. It also has better corrosion resistivity than in 0⋅177 M LiBr aqueous electrolytes. Furthermore, in order to explain the corrosion mechanism in two working fluids, the Van der Waals volume of ions and the interaction energies of ion pairs were calculated based on the density functional theory (DFT) in quantum chemistry combined with gradient corrected functional using Gaussian 09.

The corrosion of X70 steel and iron in supercritical CO₂/SO₂/O₂/H₂O environment were investigated after a 454 h exposure. Optical microscopy was applied to observe the morphology of etch pits and synthesise the three-dimensional morphology. X-ray diffraction and X-ray photoelectron spectroscopy were employed to detect the composition of product scales. Experimental results verified that the localised corrosion occurred on the X70 steel sample under corrosion product deposits. Ferrous sulphate, sulphur and iron sulphide were detected as the corrosion products.