Amount Of Corrosion Product Research Articles

Experimental investigations on corrosion resistance of innovative steel-FRP composite bars using X-ray microcomputed tomography

A steel-fiber reinforced polymer (FRP) composite bar (SFCB) is a new type of hybrid bar consisting of a steel core and an FRP shell coating. The advantages of the two materials are complementary. For example, the steel bar's good ductile properties and the FRP coating's corrosion resistance work together under tensile stress. This complementary combination provides better mechanical properties and durability than ordinary steel bars. This paper features the production of two different surface types of SFCBs, and these SFCBs' response to corrosion was accelerated by an electrochemical method encompassing three designed levels of corrosion at 5%, 15%, and 25%. The corrosion condition, including the thickness of the rust layer and the rust product distribution, was observed and qualitatively analyzed by environmental scanning electron microscopy (ESEM) and energy dispersive spectroscopy (EDS) techniques. Moreover, an X-ray microcomputed tomography (μCT) was used to investigate SFCBs corrosion, and the amount of corrosion product was quantitatively analyzed. The test results indicate that the fiber types, the micropore structure of the fiber coating layer, and the manufacturing process of the SFCBs are the main factors affecting SFCBs' corrosion resistance. The SFCBs show excellent corrosion resistance. The amount of corrosion product on the FRP coated-steel interface was much less than that of ordinary steel bars that experienced the same corrosion process. The actual corrosion rate of a carbon-type SFCB is less than 1/10 that of an ordinary steel bar, and the actual corrosion rate of a glass-type SFCB is less than 1/100 of an ordinary steel bar.

Effects of the extrusion ratio on the intergranular corrosion behaviour of 6082 aluminium alloy

The intergranular corrosion behaviour and corrosion mechanism of 6082 aluminium alloy subjected to different homogenisation processes were investigated. The results show that with increasing homogenisation temperature and/or time, the amount of corrosion product, Al(OH)3, and the thickness of its layer gradually increase, the corrosion current density decreases, and the corrosion resistance increases. In addition, the corrosion current density of the forged alloy is much smaller than that of the extruded alloy, and thus, the forged alloy is more resistant to corrosion. Two kinds of secondary phase particles, Si and AlMnFeSi, are homogeneously distributed within the plastic deformation flow lines of the alloy. When the boundary between the secondary phase Si particles and the matrix is in contact with the corrosive agent, the matrix dissolves first and initiates the formation of corrosion cracks, as the matrix serves as an anode and the Si particles serve as a cathode in the micro‐galvanic cell configuration. Moreover, the corrosion cracks develop into networks upon electrochemical corrosive coupling between the β″‐Mg2Si precipitates and the precipitate‐free zone (PFZ) located along the grain boundaries.

A probabilistic threshold for the onset of carbonation-induced corrosion

A large experimental investigation was conducted in order to assess the capability of electrochemical techniques to detect the effective onset of carbonation-induced corrosion. Specimens made with CEM I, CEM II and CEM III cement-based concrete with embedded steel bars were subjected to several exposure conditions (wet/dry cycles, partial saturation and outdoor conditions) and tested. At regular time intervals, the polarisation resistance and free corrosion potential were measured, as was the amount of corrosion product. From the data acquired, and considering the experimental uncertainties, the probabilities of right or wrong alarm were estimated depending on the alarm thresholds for the electrochemical measurements and the threshold of the effective onset of corrosion. Optimum values of these thresholds were proposed on the basis of the receiver-operating-characteristic curve concept.

Relationship between the corrosion behavior and the thermal characteristics and microstructure of Mg–0.5Ca–xZn alloys

Effects of secondary phases on corrosion behaviour of the Mg–0.5Ca–xZn alloys were investigated by polarization, immersion and hydrogen evolution tests. The Mg2Ca phase nucleated at 520°C while, Ca2Mg6Zn3 and Mg51Zn20 phases were formed at 420°C and 330°C respectively. The corrosion resistance of Mg–0.5Ca alloy was enhanced with the addition of Zn up to 1%, while further addition reversed the effect. The Mg–0.5Ca–1Zn alloys with (α-Mg+Ca2Mg6Zn3+Mg2Ca) phase showed lower corrosion rate than the alloys with (α-Mg+Ca2Mg6Zn3) and (α-Mg+Ca2Mg6Zn3+Mg51Ca20) phases. The amount of corrosion product, composed of Mg(OH)2 and hydroxyapatite on the surface of the alloy, increased with increasing Zn content.

Corrosion behaviour of Nickel‐aluminium alloys in molten carbonate

AbstractThe corrosion behaviour of nickel‐aluminium alloys with aluminium contents of 2‐50%, in molten carbonate has been investigated with electrochemical techniques in combination with post‐test analysis of quenched specimens.For the 2 to 10% aluminium alloys a type of aluminium oxide is formed along the grain boundaries of the base metal at potentials of ‐1100 and ‐900 mV. At potentials of ‐700 nmV and more anodic an outer oxide scale is formed and also aluminium oxide formation takes place along the grain boundaries. The oxide scale contained nickel, aluminium and oxygen. The only corrosion product that could he detected by X‐ray diffraction on specimens quenched after polarisation at ‐700 mV or more anodic is NiO; no type of aluminium oxide could be detected, probably due to the small amount of aluminium oxide formed.For the 20% aluminium alloy a type of aluminium oxide is formed along the grain boundaries at ‐1100 and ‐900 mV. After longer polarisation times also the aluminium in the interior of the grains is oxidised, which results in a two‐layer microstructure: an outer layer of pure nickel, and an inner layer that is a honeycomb network of nickel filled with aluminium, oxygen and nickel, while high amounts of aluminium and oxygen could be detected along the grain boundaries. The amount of corrosion product was too small to be detected by X‐ray diffraction. At potentials of ‐700 mV and more anodic, an oxide scale of irregular thickness is formed, but no oxide could be observed along the grain boundaries. The only corrosion product detected by X‐ray diffraction on specimens quenched after polarisation at potentials in this range is nickel oxide.On the 50% aluminium alloy a continuous oxide layer is formed at all potentials. The only corrosion product formed at all potentials is α‐LiAlO2; the stable form of LiAlO2 is γ‐LiAlO2. α‐LiAlO2 is probably an intermediate product that is slowly transformed to γ‐LiAlO2. The oxide layer provides good protection against further corrosion of the base material.The quasi‐stationary polarisation curves are very similar to those of pure nickel, because no protective oxide scales are formed on the 2 to 20% aluminium alloys during preconditioning at ‐1100 mV.

Initiation Behavior of Pitting in Stainless Steels by Accumulation of Triiodide Ions in Water Droplets

Abstract The initiation behavior of pitting on type 304L (UNS S30403) and type 316L (UNS S31603) stainless steels (SS) in wet air containing a slight amount of iodine (I2) was studied. The amount of corrosion product and the concentration of triiodide ions (I3−) in the product increased with time. Mass loss increased exponentially in three stages. The pitting probability obeyed the exponential law. A proportional relation was found between a kinetic parameter (G) and a stochastic parameter (λ).

Photothermal Beam Deflection Study of Titanium Metal Corrosion by a Hot Lubricant

The applicability of the photothermal beam deflection (PBD) method in monitoring the corrosion of titanium metal by a perfluoropolyether lubricant was investigated in the 21°–270°C temperature range. The signal amplitude and rise time at lower temperatures (21°–150°C) were constant for a given amount of corrosion product. At higher temperatures (150°–270°C) thermal gradients in the sample cell caused correctable distortions of the PBD signal. The signal rise times in all cases were slow (1–2 s). Signal amplitude sensitivity to thermal gradients made kinetic measurements difficult, even on a long time scale. The PBD signal indicates that corrosion depends on the presence of molecular oxygen in the lubricant as well as upon temperature.