Effect of increased temperature on erosion-corrosion under turbulent conditions in Bayer liquor

A study of the behaviour of mild steel in synthetic Bayer liquor at 25 °C and 95 °C showed that turbulent conditions had a small effect on the anodic currents at 25 °C, but caused large increases in currents at 95 °C. This may be due to the increased solubility of magnetite at the higher temperature.

Concentration monitoring and performance of a migratory corrosion inhibitor in steel-reinforced concrete

Inhibitor concentration depth profiles for concrete samples treated with a proprietary migratory corrosion inhibitor (of the Cortec MCI range) are presented. The treated concrete was cored and these cores were then sectioned and crushed before being immersed in distilled water to extract the available inhibitor. The amine concentrations were quantified using an ammonium-sensing electrode and were then related to the inhibitor concentration present. The inhibitor examined, reported to contain a combination of volatile amines and amino carboxylate compounds, was found to readily diffuse through concrete. The inhibitor was subjected to a 5-year trial and found to be effective in suppressing corrosion of steel reinforcement in the presence of high chloride concentrations. The concentration profiles indicate that only relatively low concentrations of inhibitor were required to achieve inhibition in this case.

An investigation of a phosphinate-based ionic liquid for corrosion protection of magnesium alloy AZ31

This work reports a preliminary exploration of the potential of the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (P_6,6,6,14M₃PPh) for use as a conversion coating agent for corrosion protection of magnesium alloy AZ31. Results obtained for the as received IL did not indicate any measureable improvement in protection. However, when the IL was allowed to reach equilibrium/saturation with moisture from the atmosphere, treatment with this ‘wet’ solution resulted in a substantial improvement in corrosion resistance. Preliminary electrochemical, optical, and spectroscopic characterization of the film will be presented along with a possible mechanism for film formation.

Corrosion protection of AA2024-T3 using rare earth diphenyl phosphates

Existing corrosion protection technologies for aluminium alloys utilising chromates are environmentally damaging and extremely toxic. This paper presents a preliminary investigation into rare earth diphenyl phosphates as new environmentally benign corrosion inhibitors. Full immersion weight loss experiments, cyclic potentiodynamic polarisation measurements and Raman spectroscopy were used in this study. Results show cerium diphenyl phosphate (Ce(dpp)₃) acts as a cathodic inhibitor, decreasing cathodic current density and E_corr by passivating cathodic intermetallic particles on the alloy surface. Mischmetal diphenyl phosphate (Mm(dpp)₃) acts a mixed inhibitor, shifting E_corr to more noble values, decreasing cathodic current density, increasing the breakdown potential and suppressing pitting.

Influence of praseodymium - synergistic corrosion inhibition in mixed rare-earth diphenyl phosphate systems

Mixed rare-earth organophosphates have been investigated as potential corrosion inhibitors for AA2024-T3, and previously have shown synergistic inhibition behavior; however, the mechanism was not identified. In this paper, a key factor contributing to corrosion inhibition of AA2024-T3 with mischmetal diphenyl phosphate [Mm(dpp)3] is the unique stability of Pr(dpp)3 compared to other key rare earths in mischmetal. Although increasing pH causes precipitation of other components, the Pr compound is stable at higher pH. Electrochemically, a synergy is evident when Ce(dpp)3 and Pr(dpp)3 are combined. Raman mapping indicates the Pr(dpp)3 inhibitor leads to a more uniform coverage of the alloy.

Corrosion of magnesium alloy ZE41 – The role of microstructural features

Magnesium alloy ZE41, used extensively in the aerospace industry, possesses excellent mechanical properties albeit poor corrosion resistance. This paper investigates the mechanism of corrosion and the interaction between the grain boundary intermetallic phases, the Zr-rich regions within the grains and the bulk Mg-rich matrix. The results of optical and scanning electron microscopy (SEM) together with energy-dispersive X-ray (EDX) and atomic force microscopy (AFM) potential map measurements have shown the importance of the microstructure in the initiation and propagation of corrosion in an aqueous environment, indicating that the Zr-rich regions play a distinct role in the early stages of corrosion in this alloy.

Synthesis and physical property characterisation of phosphonium ionic liquids based on P(O)2(OR)2− and P(O)2(R)2− anions with potential application for corrosion mitigation of magnesium alloys

Phosphonium cation based ionic liquids (ILs) have become of interest due to their unique chemical and electrochemical stability as well as their promising tribological properties. At the same time, interest has also grown in the use of phosphate and phosphinate based ionic liquids for corrosion protection of reactive metals. In this work we describe the synthesis and characterization of six novel ionic liquids based on the tetraalkylphosponium cation coupled with organophosphate and organophosphinate anions and their sulfur analogues. The conductivity and viscosity of these ILs has been measured and discussed in terms of the nature of the interactions, effect of anion basicity and the extent of ionic character. The reaction of the IL with a ZE41 magnesium aerospace alloy surface is also demonstrated.

Exercise performance and V0₂ kinetics during upright and recumbent high-intensity cycling exercise

This study investigated cycling performance and oxygen uptake (VO₂) kinetics between upright and two commonly used recumbent (R) postures, 65ºR and 30ºR. On three occasions, ten young active males performed three bouts of high-intensity constant-load (85% peak workload achieved during a graded test) cycling in one of the three randomly assigned postures (upright, 65ºR or 30ºR). The first bout was performed to fatigue and second and third bouts were limited to 7 min. A subset of seven subjects performed a final constant-load test to failure in the supine posture. Exercise time to failure was not altered when the body inclination was lowered from the upright (13.1 ± 4.5 min) to 65ºR (10.5 ± 2.7 min) and 30ºR (11.5 ± 4.6 min) postures; but it was significantly shorter in the supine posture (5.8 ± 2.1 min) when compared with the three inclined postures. Resulting kinetic parameters from a tri-exponential analysis of breath-by-breath VO₂ data during the first 7 min of exercise were also not different between the three inclined postures. However, inert gas rebreathing analysis of cardiac output revealed a greater cardiac output and stroke volume in both recumbent postures compared with the upright posture at 30 s into the exercise. These data suggest that increased cardiac function may counteract the reduction of hydrostatic pressure from upright ~25 mmHg; to 65ºR ~22 mmHg; and 30ºR ~18 mmHg such that perfusion of active muscle presumably remains largely unchanged, and also therefore, VO₂ kinetics and performance during high-intensity cycling.

Studies on the properties and the thermal decomposition kinetics of natural rubber prepared with calcium chloride

To evaluate calcium chloride coagulation technology, two kinds of raw natural rubber samples were produced by calcium chloride and acetic acid respectively. Plasticity retention index (PRI), thermal degradation process, thermal degradation kinetics and differential thermal analysis of two samples studied. Furthermore, thermal degradation activation energy, pre-exponential factor and rate constant were calculated. The results show that natural rubber produced by calcium chloride possesses good mechanical property and poor thermo-stability in comparison to natural rubber produced by acetic acid.

Visualisation of chemical processes during corrosion of zinc using magnetic resonance imaging

Compositional and structural changes within an electrolyte solution above an electrochemically active metal surface have been visualised using magnetic resonance imaging (MRI) for the first time. In these proof-of-concept experiments, zinc metal was galvanically corroded in a saturated lithium chloride solution. Magnetic resonance relaxation maps were taken during the corrosion process and spatial variations in both T₁ and T₂ relaxation times were observed to change with time. These changes were attributed to changes in the speciation of zinc ions in the electrolyte.

Oxygen (O2) kinetics during early recovery from peak exercise in patients with type 2 diabetes

Aims To examine the oxygen (O₂) kinetics during early recovery from peak exercise in patients with Type 2 diabetes and to examine whether oxygen O₂ recovery is associated with fasting glucose and HbA_1c in this population.

Methods Eighty-nine participants (52 men) aged 51.8 ± 7.1 years (mean ± sd) were divided into three groups: normal weight (BMI ≤ 25.0 kg/m²), overweight/obese without diabetes (BMI ≥ 26 kg/m²) and overweight/obese with Type 2 diabetes. Participants were assessed for their aerobic power (VO_2peak) on a cycle ergometer, provided a fasting blood sample and underwent a series of anthropometric measurements. Early recovery period was measured for 60 s from cessation of exercise and expressed as percentage of VO_2peak (higher percentage represents slower recovery).

Results No significant differences were observed for age between the three study groups. Both the overweight/obese groups without diabetes and with Type 2 diabetes had higher BMI than the normal weight group, with no significant differences between overweight/obese participants without diabetes and those with diabetes. Participants with Type 2 diabetes had lower VO_2peak than overweight/obese participants without diabetes and normal weight individuals (19.6 ± 4.8, 22.6 ± 5.4 and 25.7 ± 5.3 ml kg⁻¹ min⁻¹, respectively, P < 0.004 for overall trends). Participants with Type 2 diabetes also had slower recovery in oxygen O₂ kinetics after exercise, compared with both normal weight and overweight/obese individuals without diabetes (56.5 ± 7.7, 49.2 ± 7.2, 47.7 ± 7.4%, P < 0.004 for overall trends). Multiple regression analysis revealed that percentage of oxygen O₂ recovery was a stronger predictor than VO_2peak, BMI or age for fasting glucose and HbA_1c.

Conclusions Patients with Type 2 diabetes have lower VO_2peak and prolonged oxygen O₂ recovery from peak exercise. However, only prolonged oxygen O₂ recovery was associated with fasting glucose and HbA_1c.