1,720,983 research outputs found
Monitoring degradation of single and multilayer organic coatings. I. Absorption and transport of water: Theoretical analysis and methods
No full textThis paper presents a mathematical model describing the change in the capacitance of both single and multilayer organic coatings exposed to a wet environment. The indication is that the capacitance technique can successfully be employed to monitor, in situ, the absorption of water through single-layer organic coatings for values of equilibrium water uptake to a maximum of 5% by volume. In addition, this model indicates a relationship for d(In C)/d√t, where C is the coating capacitance and t is the time of exposure to the environment, that can be used to rank different single-layer coatings. Conversely, no quantitative correlation between mass uptake and coating capacitance was found for a multilayer coating system, even for low values of water uptake. Although, at face value, these findings suggest that this technique may be inappropriate for in situ monitoring of water absorption in such complex systems, a comparison between gravimetric and capacitance data indicates that useful qualitative information may still be generated by the use of the latter technique
The Relationship Between Substrate Mass Loss Assessed by Vibrating Sample Magnetometer and Corrosion Rate Measured by Electrochemical Impedance Spectroscopy for a Polymer-Coated Metal
No full textTHE WET CORROSION OF MOLYBDENUM THIN FILM - PART I: BEHAVIOR AT 25°C
No full texthe corrosion and passivation behaviour of molybdenum thin films obtained by Physical Vapor Deposition (PVD) was investigated in aerated chloride and sulfate solutions at different pH values. Open circuit potential (ocp) measurements, polarisation experiments and electrochemical impedance spectroscopy (EIS) were employed. The experimental results suggest that the metal surface is covered by a passive film; however, corrosion still occurs. For the samples assessed during the current research, the acidic electrolytes tended to be less corrosive; however, a limited passive region was associated with the most basic sulfate or chloride solution. The effect of the pH was found to be more pronounced than the effect of the ion (chloride or sulfate)
The wet corrosion of molybdenum thin film - Part III: The effect of Ti and Nb
No full textMagnetron sputtering has become the process of choice for the deposition of a wide range of industrially important coatings. Over the last decade, interest in molybdenum thin films prepared by magnetron sputtering has been increasing; however, little research has been done on molybdenum-titanium and molybdenum-niobium alloy thin films. During the current study, electrochemical impedance spectroscopy (EIS) was employed to investigate the effect on the corrosion resistance in basic chloride environments of adding titanium and niobium species to molybdenum thin films deposited by physical vapor deposition. The results indicate that the MoTi alloy thin films exhibit better protective properties than either the molybdenum-niobium alloy or unalloyed molybdenum thin films
A NEW APPROACH IN THE MONITORING OF METAL COUPON SUBJECTED AT FATIGUE LOAD IN AGGRESSIVE SOLUTION
No full textCorrosion fatigue (CF) is defined as the sequential stages of metal damage that evolve with accumulated load cycling, in an aggressive environment, and resulting from the interaction of irreversible cyclic plastic deformation with localized chemical or electrochemical reactions. The pitting fatigue corrosion (PFC) is a part of CF that studies the influence of fatigue and aggressive environment on pit creations and crack generation and propagation, up to catastrophic failure.
It appears then evident the need to know and understand all phenomena that are involved in pit formation and growth in presence of both an aggressive environment and a cyclic load. Although each single effect of both fatigue and corrosion have been extensively documented for aluminium alloys, their synergic action is not thoroughly understood and it continues to be an area of considerable scientific and industrial interest. Fatigue experiments were conducted on bare AA 2024 T3 aluminium alloy specimens in presence of an aggressive environment consisting of a water aerated solution with 3.5 % of NaCl in weight. The mechanical stress was imposed on simple cantilever beam way in high-cycle fatigue.
Strain and Open Circuit Potential (OCP) variations observed as a functions of number of cycles are interpreted as a result, and taking into account, the numerous and complex phenomena occurring as time goes on. The pits birth and their subsequent growth seem to play a significant role as crack initiation and subsequent propagation up to final catastrophic failure
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