Search results for " Protection"
showing 10 items of 995 documents
In situ investigation of sacrificial behaviour of hot dipped AlSi coating in sulphate and chloride solutions
2013
Abstract The electrochemical behaviour of the cut-edge of hot-dipped aluminium–silicon-based alloy coated steel is studied in immersed conditions in sulphate and in chloride media. Preliminary studies performed on steel-pure Al bi-electrode demonstrate that a significant galvanic current can develop at short times (t
Modeling bimetallic corrosion under thin electrolyte films
2011
A finite element model (FEM) was developed to calculate the potential distribution in the electrolyte in the case of bimetallic corrosion between iron and zinc electrodes, taking into account mass transport of oxygen in the solution. This model was first compared with experimental results obtained by scanning vibrating electrode technique (SVET) on a galvanized steel cut-edge in immersion conditions in a 0.03 M NaCl electrolyte. A good agreement was obtained between the calculated and experimental current densities. The model predicted the evolution of the galvanic coupling as function of the electrolyte thickness and for various iron–zinc surface area ratios. Different coupling regimes wer…
Protective mechanisms occurring on zinc coated steel cut-edges in immersion conditions
2011
Abstract Electrochemical processes occurring on the cut-edge of a galvanized steel immersed in NaCl solutions were studied using numerical simulations, and in situ current and pH profiles measured over the cut-edge. These results clearly demonstrate that only the steel surface remote from the zinc coating is cathodically active, oxygen reduction being strongly inhibited in the vicinity of zinc. This trend was confirmed by local polarization curves recorded on these distinct areas. Ex-situ AES and SEM analysis and cathodic polarization curves in solutions containing Zn 2+ ions led to conclude that this cathodic inhibition was related to the fast nucleation of a dense Zn(OH) 2 film on the ste…
Investigation of self-healing mechanism on galvanized steels cut edges by coupling SVET and numerical modeling
2008
Local cathodic inhibition has been observed on the cut-edge of galvanized steel immersed in 0.03 M NaCl solution using the scanning vibrating electrode technique. The current distribution results indicate that cathodic inhibition occurs in a limited spatial zone located between the cathodic sites on the steel and the anodic sites on the exposed zinc surface. The experimental current distributions are compared with the results of numerical simulations that show the specific diagnostic features for the detection of cathodic inhibition from scanning vibrating electrode technique (SVET) data so as to distinguish the zero current regions from experimental artifacts due to the lateral resolution …
Influence of plastic deformation on the microstructure and corrosion behaviour of Ti–10Mo–4Zr and Ti–6Al–4V alloys in the Ringer’s solution at 37°C
2015
Abstract The influence of plastic deformation on the microstructure and passivity of Ti–6Al–4V and Ti–10Mo–4Zr is studied. The content of titanium-based compounds in the passive film formed on the alloys increases under straining. In the region where necking occurs, the β-phase content drops in Ti–6Al–4V. The grain orientation spread increases with increasing strain. The quality index of EBSD maps is affected on Ti–10Mo–4Zr (dislocation structures along preferential orientations). The corrosion behaviour is investigated in the Ringer’s solution (37 °C). Results obtained in the anodic and cathodic domains are discussed considering changes described previously.
Mechanical properties and corrosion behaviour after scratch and tribological tests of electrodeposited Co-Mo/TiO2 nano-composite coatings
2019
International audience; The micro-mechanical (Young’s modulus and hardness) and tribological properties, as well as the scratch resistance of Co-Mo/TiO2 nano-composite coatings were investigated. The coating was found to be harder and stiffer than the substrate (pure cobalt). Low residual stresses were also derived from Stoney’s equation (type I stress). The corrosion behaviour after tribological and scratch tests was studied in Ringer’s solution. Dry sliding of the coating against an alumina ball at the load of 1 N or 2 N over the same distance had nearly no influence onthe anodic branch of the polarisation curves. By contrast, the current density in the cathodic branch (oxygen reduction r…
Pulsed laser cleaning of oxidized metallic surfaces in electrochemically controlled liquid confinement
1997
Pulsed laser cleaning of oxidized metallic surfaces is studied. To our knowledge, for the first time, it has been demonstrated that the application of pulsed laser irradiation in a liquid confinement at controlled electrochemical potential enhances the oxide film removal from metal surfaces. Systematic studies on simulated corrosion product films using optical reflectance profile, energy dispersive X-ray spectroscopy, and piezoelectric transducer measurements, have revealed that efficient oxide film removal by laser irradiation is achieved if a basic electrolyte solution is used and a cathodic potential is imposed. The advantages of this novel technique against laser irradiation in air are …
Synthesis of self-standing Pd nanowires via galvanic displacement deposition
2009
This work shows that it is possible to obtain self-standing Pd nanowires into anodic alumina membranes by a simple metal displacement deposition. By using a proper arrangement, specifically designed in order to optimize the process, polycrystalline Pd nanowires were deposited from a solution containing Pd(NH3)4(NO3)2 as precursor. Morphological analysis showed the formation of perfectly aligned nanowires with a uniform diameter throughout the entire length. This last parameter was controlled by both the deposition time and the ratio between the anodic area (active metal) and the cathodic area (pore bottom). Keywords: Displacement deposition, Template synthesis, Palladium nanowires, Alumina …
Use of the electrochemical microcell technique and the SVET for monitoring pitting corrosion at MnS inclusions
2004
The purpose of this paper is to report on use of the electrochemical microcell technique and the scanning vibrating electrode technique for monitoring pitting corrosion on the same stainless steel microstructure. First, the electrochemical behaviour of sites containing a single inclusion was investigated in order to the determine both the successive steps occurring during the inclusions activation and some key-parameters such as the onset potential for MnS dissolution and the pitting potential. Then, the local current distribution around a pitting site was monitored at open circuit potential in order to locate anodic and cathodic regions and to obtain informations on the galvanic coupling b…
Electrochemically-induced TiO2 incorporation for enhancing corrosion and tribocorrosion resistance of PEO coating on 7075 Al alloy
2018
Abstract 7075 Al alloy was PEO-treated in a silicate based electrolyte containing 3 g l-1 potassium titanyl oxalate using unipolar and bipolar pulsed current waveforms. The coating formed by the bipolar waveform with the wider cathodic pulses showed volcano-like surface morphology with no evidence of large pores at the metal/coating interface. It revealed the highest corrosion performance due to the synergistic effect of TiO2 incorporation and structural/morphological features along with a better passivation behavior indicating no pitting susceptibility. For this coating, the tribocorrosion tests showed no potential drop during sliding under 1 N with the lowest volume loss of 0.022 mm3.