Abstract The inhibition effect of Cefalexin on mild steel corrosion in sodium chloride has been examined with the use of electrochemical potentiodynamic polarization techniques, weight loss measurements and computational studies. Cefalexin showed good protection ability by adsorbing onto the mild steel surface. The mixed inhibition characteristics of Cefalexin were revealed by the potentiodynamic polarization results. The inhibitor efficiency was found to be above 65%, obeying the Langmuir and Freundlich isotherm law, with a correlation regression coefficient of R2= 0.9984 and R2= 0.9488, respectively, establishing the reliability on Cefalexin as an inhibitor.

Abstract Ti10Fe5Si5Cr3Nb composite coatings were fabricated using laser cladding technique. Laser power was varied from 800W to 1200W while the scanning speed was kept constant at 1.5 m/min. The microstructural analysis of the samples was conducted by using optical microscope, X-ray diffractometer and scanning electron microscope coupled with energy dispersive spectroscopy. Potentiodynamic polarization and diamond indenter were used to study the corrosion and microhardness properties of the alloy. The alloy exhibited a dendritic microstructure with Si-rich dispersed phase. Grain coarsening was observed to be dependent on coating depth. The microhardness was high at the top and decreased with coating depth. No improvement in corrosion resistance was noticed but the presence of Cr in the alloy promoted passivation.

Coating is a technology for improving the surface properties of components. Laser coating produces uniform composition with thickened layers that display a good metallurgical bond to the base material. These coatings are dense and crack-free, and have non-porous microstructures. The advantages of the process are that the components' surface will have high resistance to wear and corrosion, even at elevated temperatures. In this work, Ti6Al4V base material was coated with zirconium and zirconia composite material to improve the base material's resistance to corrosion and wear. Zirconium powder mixed with binder (PVA and cold glue) was melted to produce a thin layer, which was then bonded to the Ti6Al4V by irradiation with a fibre laser, thus forming a zirconium + zirconia composite due to an in-situ reaction in the liquid state. The presence of binder in the Zr powder indicated a change in the microstructural behaviour, as the results showed a gradual increase in the hardness of the coated Ti6Al4V from top to bottom. It was also found that Zr + PVA binder coating was uniformly deposited, and had a less dendritic structure compared with Zr without binder or Zr with cold glue.

Oppervlakbedekking is 'n tegnologie wat die oppervlak-eienskappe van komponente verbeter. Laseroppervlakbedekking verskaf 'n uniforme samestelling van dik lae met goeie metallurgiese hegting aan die basis materiaal. Hierdie bedekkings is dig en kraakvry en het nie-poreuse mikrostrukture. Die voordele van die proses is dat die komponent se oppervlak 'n hoë weerstand teen slytasie en korrosie het, selfs by hoë temperature. Ti6Al4V basis materiaal word in dié studie bedek met Zr en ZrO2 samestellings om die komponent se weerstand teen korrosie en slytasie te verbeter. Zr-poeier wat gemeng is met 'n verbinder (PVA en koue lym) is gesmelt om 'n dun lagie te vorm. Die lagie is gebind aan die Ti6Al4V component deur bestraling met 'n vesellaser. Die teenwoordigheid van die verbinder in die Zr-poeier het gelei tot 'n verandering in die mikrostruktuur, die resultate toon 'n geleidelike toename in die hardheid van die bedekte Ti6Al4V van bo na onder. Daar is ook gevind dat die bedekking met die Zr saam met die PVA verbinder uniform gedeponeer is en 'n minder dendritiese struktuur gehad het as die Zr sonder binder of die Zr met die koue lym.

Laser coatings are used for a wide variety of applications. TiB2/Ni intermetallic matrix composite coatings were fabricated on Alsubstrate by a high power Rofin Sinar Nd: YAG solid-state laser. The characterization of the coatings was carried out by optical microscopy (OM), scanning electron microscopy (SEM/EDS) and Xray Diffraction (XRD). Electrochemical study of the laser coatings in 3.65 per cent NaCl at room temperature revealed that with very high weight proportion of nickel the corrosion resistance of the coatings deteriorated due the presence of AlB10 phase. 50 wt per cent TiB2+50 wt per cent Ni laser coatings exhibited the highest corrosion resistance in test solution.

Aluminium AA1200 was laser alloyed with a combination of nickel and titanium diboride using different weight ratios. Chemical reactions took place with the formation of different phases. The characterization of the alloyed surfaces was carried out by x-ray diffraction (XRD), optical and scanning electron microscopes. The alloyed surfaces are composed of the initial phase of Al-Ni dendrites and eutectics of TiB2/Al and TiB2/Ni distributed on the initial phase. Experimental results obtained showed that Al-Ni intermetallics brought about a significant increase in the hardness property of Al; however, these intermetallics are highly brittle and prone to fail by brittle fracture or stress corrosion cracking when put in service. The addition of TiB2 brought about a reduction in the formation of these intermetallic phases. A microhardness increase of over 10 times the hardness of the substrate was achieved.