Influence of laser power on the corrosive behavior of laser metal deposited Ti6Al4V+Cu in artificially prepared sea water

Titanium alloy is an excellent corrosion resistance material due to its greater affinity with oxygen when exposed to an aggressive medium such as sea water. The protection against attack is due to the oxidizing fume formed into its surface. This paper reports the effect of laser power on the corrosive behavior of laser metal deposited Ti6Al4V alloy with 5 weight percent (wt. %) copper in freshly prepared artificial sea water. The open circuit potential, potentiodynamic polarization curves, and the scanning electron microscope (SEM) morphologies of the entire Ti6Al4V+5 Cu alloy samples had been investigated and reported. From the results obtained, it can be deduced that the laser power is inversely proportional to the corrosion rate. Sample PL3 deposited with a laser power of 1600 W exhibited the best corrosion rate of 0.0123 mm/year when exposed to sea water under aerated condition. The morphologies of the entire laser deposited samples of the scanning electron microscope (SEM) unveiled typical passivity due to the strong inter-atomic bonds between the α/β phases formed with the copper inclusion within the lattices of the titanium alloy.     

Influence of interface-related parameters on some heat stable salts in the corrosion studies of carbon steel for post-combustion CO2 capture

The effect of flow and temperature on the corrosion behavior of carbon steel in an aqueous methyldiethanolamine solution containing different heat stable salts, such as sodium sulfate, sodium sulfite and sodium thiosulfate, has been studied. The introduction of flow and increase in temperature generally caused an increase in the corrosion rate of carbon steel but the presence of the heat stable salts affected the corrosion behavior to different extents. Sulfate increased the corrosivity of the aqueous methyldiethanolamine solution, thus showed accelerated corrosion behavior in the presence of flow and with increase in temperature when compared with the solution without heat stable salts. The presence of sulfite reduced the corrosivity of the methyldiethanolamine solution due to its oxygen scavenging ability. Although flow and temperature stimulated an increase in the corrosion rate of carbon steel, the corrosion inhibiting effects of sulfite ions increased with the salt concentration. Also, the presence of sodium thiosulfate caused a reduction in carbon steel corrosion. Its inhibition ability is largely the result of the formation of FeS product layer resulting from its disproportionation reaction. This layer offered a slight resistance to the influence of flow and increase in temperature when compared with the system without heat stable salts.     

Measurement system for long-term recording of wood moisture content with internal conductively glued electrodes

Moisture as an important influence factor on fungal growth needs to be considered for service life prediction of wood and wood-based products. Therefore, a long-term moisture measuring and data logging method for wood in weathered conditions was developed. The method is based on measuring the electrical resistance with glued electrodes for sustainable connection. The measuring point at the tip of the electrodes was glued conductively into the wood, the remaining outer part of the electrodes was glued with an isolating glue. For this purpose, special conductive and isolating glues and electrodes were developed and comparatively evaluated in laboratory tests. The most suitable system consisted of a 2k-epoxy resin, serving for the isolating glue and also as conductive glue (when mixed with graphite powder and ethanol) in combination with a partly isolated stainless steel cable, acting as both, electrode and cable. This system was further tested in combination with mobile mini data logger at 29 different exposure sites in Europe and the United States. After 4–6 years of natural weathering with many extreme climatic and moisture changes, no loosening or other detectable abnormality in 541 pairs of electrodes was observed. The data logging systems were working without any problems for 5 years with the first and only battery, and without any additional maintenance. For the calibration of the measuring system, resistance characteristics were determined for different provenances of Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies Karst.), and Douglas fir (Pseudotsuga menziesii Franco).     

The effect of molybdenum on the corrosion behaviour of the high-entropy alloys Co1.5CrFeNi1.5Ti0.5Mox in aqueous environments

The purpose of this study is to investigate the electrochemical properties of the Co_1.5CrFeNi_1.5Ti_0.5Mo_x high-entropy alloys in three aqueous environments which simulate acidic, marine, and basic environments at ambient temperature (∼25 °C). The potentiodynamic polarisation curves of the Co_1.5CrFeNi_1.5Ti_0.5Mo_x alloys, obtained in aqueous solutions of H₂SO₄ and NaOH, clearly revealed that the corrosion resistance of the Mo-free alloy was superior to that of the Mo-containing alloys. On the other hand, the lack of hysteresis in cyclic polarisation tests and SEM micrographs confirmed that the Mo-containing alloys are not susceptible to pitting corrosion in NaCl solution.     

Electrochemical effect of Copper Gleam additives during copper electrodeposition

Electrochemical nano and micro fabrication by flow and chemistry is a maskless micro-patterning technology that uses an acid-free and low ion concentration electrolyte. However, the effects of additives on the electrochemical behaviour of this type of electrolyte are still unknown; hence, their role during micro- and nano-fabrication is unpredictable. This study reports the effect of a suppressor (Copper Gleam B), an accelerator (Copper Gleam A) and a promoter (Cl^?) on the electrochemical behaviour of copper reduction. The three additives, when employed separately, were found to increase cathode polarisation. The combination of Copper Gleam B and Cl^? showed strong inhibition, particularly in the diffusion-limited region. The addition of Copper Gleam A to the Copper Gleam B–Cl^? mix increased the limiting current and suggested plating acceleration. These effects are interpreted in terms of the adsorption–desorption behaviour of the additives on the cathode surface.     

Development of carbon nanotubes reinforced hydroxyapatite composite coatings on titanium by electrodeposition method

Carbon nanotubes (CNTs) are outstanding reinforcement material for imparting strength and toughness to brittle hydroxyapatite (HAP). This work reports the electrodeposition of CNTs reinforced HAP on titanium substrate at −1.4 V vs. SCE during 30 min with the functionalised CNTs concentration ranging from 0 to 2 wt.%. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX), high resolution transmission electron microscopy (HRTEM), mechanical and biological studies were used to characterise the coatings. Also, the corrosion resistance of the coatings was evaluated by electrochemical techniques in simulated body fluid (SBF) solution.     

Influence of tempering treatment on microstructure and pitting corrosion resistance of a new super ferritic–martensitic–austenitic stainless steels with 17%Cr

Supermartensitic stainless steels (SMSSs) allow high mechanical strength with better corrosion resistance and toughness than conventional martensitic stainless steels. The SMSS steels with 12–13%Cr have been studied and applied in the oil and gas offshore production. The increase of Cr content, and the addition of Mo and W is now being investigated to increase mechanical and pitting corrosion resistance. In this work, a new 17%Cr steel, with Mo and W additions was studied. Depending on the final tempering treatment, the steel has a complex microstructure of austenite, ferrite, martensite and precipitates. The pitting corrosion resistance also depends on the microstructure produced by tempering. It was found that the pitting potential slightly decreases with the increase of tempering temperature and is further decreased by the double-tempering treatment. The pits initiate and grow preferentially in the martensite or tempered martensite islands, due to the lower Cr, Mo and W contents of these areas.     

Prediction of the Suitability of the Weather Conditions for External Painting: A painting weather map

Abstract

A statistical study was made of weather records from four sites, Prestwick, London (Heathrow), Manchester (Ring way) and Cardiff (Rhoose) for the period 1959–68, to determine the distribution of normal working time that was judged unsuitable for painting, according to B.S. Codes of Practice. The results show the expected seasonal bias with frequent unsatisfactory days in November to March. There were large variations between sites, Cardiff being markedly worst, and between individual years. It is suggested that studies of this kind could form the basis for fixing lost time premiums on the cost of winter painting contracts.     

Feasibility of determining corrosion rates by means of stray current-induced polarisation

To measure metal corrosion it is necessary to make direct physical contact with the specimen or component acting as the working electrode. The most widely used method for determining the corrosion current is electrochemical, the so-called polarisation resistance method. The feasibility of a new method to polarise the metal without the need for direct physical contact was investigated in the present study. The required potential shift is obtained by induction of a current using an external electrical field. The model used for calculation of the corrosion rate assumes that the applied current runs in parallel through the electrolyte and the metal, and electrostatically polarises the metal. The overall electrical resistance of the system can then be expressed as , where R _e+M is the total resistance measured, R _e is electrolyte resistance and R _M is resistance due to the metal. This latter resistance to electrostatic polarisation is related to the faradaic reaction, which was verified by comparison with the gravimetric losses. This resistance has been called inductive polarisation resistance R _pi to distinguish it from the traditional polarisation resistance R _p.     

X-ray scattering in X-ray fluorescence spectra with X-ray monochromatic, polarised excitation - Modelling, experiment, and Monte-Carlo simulation

A systematic series of measurements has been carried out with monochromatic X-ray excitation with synchrotron radiation in order to check a physical model on X-ray scattering. The model has recently been successfully tested for the case of polychromatic, unpolarised excitation emitted by an X-ray tube. Our main purpose is the modelling of a physical background in X-ray fluorescence spectra, so that improved quantitative results can be achieved especially for strongly scattering specimens. The model includes single Rayleigh and Compton scattering in the specimen, the effect of bound electrons, the challenging Compton broadening and the polarisation degree. Representative specimens, measurement geometries and excitation energies have been selected with synchrotron monochromatic light at BAMline/BESSY II. Monte-Carlo simulations have been also carried out in order to evaluate the quality of the results achieved with the model.