Commercial pure (CP) titanium has many applications in biomaterials especially in implants due to its excellent biocompatibility. Despite the importance of surface properties in bio-applications, limited research has been conducted to improve surface properties of CP titanium by improving the structure. Therefore, the purpose of this research is to improve the corrosion and wear properties of CP titanium by reducing grain size by multi-directional forging (MDF) process. For this purpose, annealed CP titanium samples were forged by MDF up to six passes at ambient temperature and 220°C. To investigate the corrosion properties of specimens, the tafel polarization test was performed in a simulated body fluid (SBF) solution. The tribological properties were also investigated by pins-on-disk test at sliding speed and applied stress of 0.2 (m/s) and 1MPa, respectively. The results of microstructure analysis of the samples using a scanning electron microscope (SEM) equipped with EBSD showed that the ultrafine grain structure was formed in titanium CP, after 6 passes of the MDF. The results of the investigation of the tafel polarization test showed that the corrosion resistance of the samples increased with applying MDF and increasing the pass number, regardless of the processing temperature. Also, the corrosion resistance of MDFed samples at 220°C temperature was higher than the MDFed samples at ambient temperature. Wear resistance of CP titanium was also increased, by decreasing the grain size. The results of the investigation of surface morphology of samples using a field-emission scanning electron microscope showed mainly the abrasive and delamination wear mechanisms.

The aim of this study was to investigate the effect of Ti addition on corrosion behavior of IN625 surface clad layer fabricated by Tungsten inert gas (TIG) welding. For this purpose a layer of IN625 was cladded on plain carbon steel and pure Ti was subsequently embedded into the clad layer by TIG surface welding. According to Ti content added by surface welding clad layers containing 29 and 39 wt.% Ti were obtained. Microstructural investigations of clad layers were conducted by optical microscopy (OM). Potentiodynamic polarization testing was used to study the corrosion behavior of the clad layers. Cyclic polarization experiments showed improved corrosion resistance of resultant Ni-Ti layer compared to that of IN625 clad layer. Surface clad layer containing 39 wt.%Ti showed a repass potential (Ep) of 1.5 V higher than that of IN625 with the highest pitting resistance among fabricated clad layers.

Plasma Electrolytic Oxidation (PEO) method was employed to enhance corrosion resistance of 7075 Aluminum alloy. The coating process carried out in a silicate based electrolyte by DC constant current density. Characteristics of coating were evaluated by X-ray diffraction and scanning electron microscopy methods. Analysis showed the formation of γ-alumina oxide film, which has a porous surface and some pores in its structure. Coating corrosion behavior was evaluated by electrochemical tests after 1 hour immersion in 1M H2SO4. Tafel Polarization test revealed that PEO decreased the corrosion current density as ten orders of magnitude, and increased the charge-transfer resistance as twenty five order of magnitude, and thus improved corrosion resistance of 7075 Al alloy. Electrochemical Impedance spectroscopy (EIS) test revealed that the coating formed a physical barrier against the charge transfer, and decreased the diffusion rate of the corrosive solution due to its non-columnar structure.

In this research, super-hydrophobic surfaces were made on pure aluminum (92%) using two methods of chemical etching, and onestep anodizing and modification with materials with low surface energy. After creating a uniform roughness on the surfaces, surface modification was done with perfluoroactyltrichlorosilane (PFTS). The wettability was investigated by measuring the drop contact angle (WCA) and the morphology of the coating with a field emission scanning electron microscope (FESEM). The chemical composition of the surface was detected by Fourier transform infrared spectroscopy (ATR-FTIR). The self-cleaning property with coal powder was investigated. Corrosion behavior was evaluated using Tafel polarization test and salt fog. The results of the water contact angle showed that the surface roughness due to anodizing and chemical etching reduced the contact angle to 15ᵒ and 24ᵒ, and after modifying the surfaces, the contact angle increased to 157ᵒ and 153ᵒ. After modifying the surface of the anodized sample, it has higher corrosion resistance than the etched sample. The final coating is self-cleaning.

In the present study, nanocrystalline Nickel-Cobalt coating was electrodeposited by pulse current from a Watts bath. Electrodeposition was carried out in the current densities of, 4, 6 A/dm at different frequencies and on-time periods in the baths containing of 0.5,, g/l saccharin. Morphology, analysis and crystallography of the coating were studied by means of SEM, EDS and XRD methods, respectively. The grain size of the coating was also calculated from XRD patterns using Scherrer equation. The results of polarization tests carried out in. 5% NaCl solution indicated that by increasing the cobalt content in the coating, although the corrosion potential slightly shifted to more negative values, but the corrosion rate decreased, which can be related to more activity of cobalt with respect to nickel. A decrease in grain size of the coating increased the corrosion rate and shifted the corrosion potential to more positive values.

Titanium dioxide and Hydroxyapatite were simultaneously added to plasma electrolyte nitrocarburizing bath of 316L stainless steel in order to improve the corrosion behavior of steel. Then the samples were placed in the electrolyte and biased with a negative voltage of 145 volt. Cross section and surface morphology were studied using a scanning electron microscope (SEM). The results of EDX and XRD analysis reveal the presence of Titanium، Calcium، Phosphorus، Nitrogen and Carbon. Corrosion behavior of the coating was investigated by tafel polarization tests in Ringer solution. The composite coating exhibits an improvement in corrosion behavior.

In the present study, Ni-P coatings were successfully deposited on mild steel surface via electroless plating. The optimization of heat treatment parameters (i.e., temperature and time) based on response surface methodology has been systematically studied in order to obtain the simultaneously improvement in corrosion resistance and hardness. X ray diffraction analysis (XRD), scanning electron microscopy (SEM) and EDS analysis were used to characterize the coatings. The corrosion behavior of the coatings was evaluated using Tafel polarization method in 3.5 wt.% NaCl aqueous solution. It has been found that the as-plate coating has an amorphous structure and heat treatment caused to precipitate Ni3P phase as well as to form crystalline nickel phase. The corrosion resistance and hardness are strongly affected by heat treatment. By increasing the time and temperature corrosion resistance and hardness firstly increased and then decreased. The results showed that low corrosion rate less than 2 mpy and high hardness value more than 900 vickers were achieved by heat treatment at 450° C for 75 min.

In this paper, the effect of tool rotation speed on the mechanical properties and corrosion behavior on dissimilar joints Friction Stir Welds between 5083 Aluminium alloy and pure Titanium is investigated. At first, with primary welding parameters range necessary to achieve suitable connection obtained and then by changing tool rotation speed, mechanical and corrosion properties of heat affected zones, welding zones and cross section zones, by using polarization Tafel test and Electrochemical Impedance Spectroscopy was investigated and the result were compared. the result indicates that corrosion behavior of connections, is impressionable of the tool rotation speed and welding zone and heat affected zones have weaker corrosion resistance compared to the base metals.

In this research, Ni-Cu/Al2O3 composite coatings were prepared by electrodeposition from a citrate-ammonia bath; and the effect of deposition current density on the microstructure, hardness and electrochemical corrosion behaviors of the coatings was studied. The results showed that the morphology and composition of the coatings are changed with the current density. Also, by increasing the current density, the microhardness of the coatings is enhanced and then decreased; whereas the corrosion resistance of the prepared coatings is progressively decreased.

In this study, the effect of input heat of SMAW process on the microstructure and corrosion behavior of welded metal API 5L X65 steel joints coated with INCOLOY 825 superalloy was investigated. Welding with input heat of 1.03, 0.99 and 0.94 kJ / mm was performed using E7018 filler metal by SMAW process. FESEM scanning light and electron microscopy was used to study the microstructure. Evaluation of corrosion behavior of weld metal was performed using TOEFL polarization test in 3.5% NaCl solution. The microstructural results showed that the needle ferrite in the weld metal microstructure decreased with increasing inlet heat. While the values of Wiedmann Statten ferrites are multifaceted and grain boundaries. It was found that increasing the inlet heat had a negative effect and reduced the corrosion resistance of the weld metal.