Superalloy IN738LC is categorized as one of the most frequently utilized nickel base superalloys in the production of hot section components due to its multiphase microstructure maximizing its strength under elevated temperatures. In this study, a hot dip diffusion coating of aluminum was employed on the nickel-base superalloy Inconel 738LC substrate to enhance the hot corrosion resistance required for high-temperature applications, such as turbine blades. The aluminizing salt bath included Al powder with a particular composition, NaCl, KCl, Na3AlF6, and NaF. A thickness of about 48 µm was attained by applying the coating for 30 minutes at 720 °C. Bare and aluminized coated specimens were subjected to hot corrosion assessment in molten salt, with a composition of Na2SO4-25wt% NaCl at 720 C being exposed for 60 and 140 hours. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) were conducted on the coating sample to ensure the successful deposition of the hot dip aluminized layer. The aluminized sample exhibited excellent corrosion resistance owing to the formation of an Al2O3 layer, which meant that after 140 hours of testing; very little coating deterioration was detected. In contrast, the naked sample suffered severe degradation and showed poor hot corrosion resistance. It was thought that the aluminized sample's superior hot corrosion resistance resulted from the uniform and dense growth of an Al2O3 protective scale without any cracks on the superalloy surface

In this study, corrosion resistance of ordinary (non-skin passed) and skin passed hot-dip galvanized steel sheets produced in Mobarakeh steel company was compared with each other. For this reason, lead content of the zinc bath was changed from 0.01 wt.% to 0.11wt.% and the corrosion resistance of the sheets was analyzed. Also, to study the effects of skin pass rolling on the corrosion resistance of the sheets, two skin passed specimens obtained from zinc baths of 0.045 and 0.065 wt.% of lead content were studied. Effect of lead content of the zinc bath and skin pass rolling on (00.2) basal texture component were also investigated. Relative intensity of (00.2) basal texture component was determined using XRD whilst the corrosion behaviour was analyzed employing Tafel polarization test. Results showed that increasing the lead content of the zinc bath would decrease the corrosion resistance and (00.2) basal texture component relative intensity of ordinary coating and conversely, increase the spangle size and darkness of the coating surface. Investigation on the effects of skin pass rolling on the galvanized sheets indicated that in this case, relative intensity of (00.2) basal texture component and spangle size have been decreased and some cracks created in the coating. In addition, it was seen that the corrosion resistance of skin passed specimens, in comparison with ordinary specimens, has been decreased.

In this research, effects of some production parameters such as lead content of the zinc bath, jet wipers distance from sheet surface and galvanizing line speed on corrosion behaviour and structure of hot-dip galvanized coating produced in Mobarakeh Steel Company was investigated. Lead content of the zinc bath was changed in the range of 0.01 to 0.11Wt.% and its effects on the texture and corrosion behaviour and spangle size was studied. Coating texture was determined using X-ray diffraction and Corrosion behaviour of the coating was analyzed employing salt spray and Tafel polarization test. Then, influences of increasing the lead content of the zinc bath, variations of jet wipers distance from the sheet surface and galvanizing line speed on the coating structure were assessed. Results showed that increasing the lead content of the zinc bath, has decreased the relative texture coefficient of basal component and conversely, has increased the relative texture coefficient of high angle pyramids, low angle pyramids and prism plane components. Also, it was discerned that increasing the lead content of the zinc bath would result in the increase of spangle size and number of dull spangles in the surface. After investigation of the effects of increasing the lead content of the zinc bath, increasing the jet wipers distance and decreasing the galvanizing line speed, it was found that gamma layer thickness, the detrimental layer for corrosion resistance and formability, has been increased.

Application of Fe-TiO2 photocatalysis using sol-gel method by hot-dipping technique was investigated. The influences of fabrication parameters; molar ratios of Fe to TiO2, the sol temperature, poly ethylene glycol (PEG) content and the number of dipping cycles on the photocatalytic activity in visible light region were studied. Results revealed that a higher photocatalytic performance of Fe-TiO2 films could be achieved using the molar ratio of Fe to TiO2: 0.015, the sol temperature: 70oC, PEG content: 2 wt. % and 5 dipping cycles. The photodegradation efficiency of this sample after 2 h of visible light irradiation increased up to 80% and no crack was detected on the surface of the thin film. When the sol temperature increased from 25 to 70oC (the boiling point of the sol), its viscosity increased due to the presence of PEG via forming cross linkage. This phenomenon resulted in the change of the coating microstructure and the improvement the optical properties.

In this paper, bare spot defects in hot-dip galvanized sheets were studied in terms of the microstructure and their influence on the corrosion and mechanical properties. Surface characteristics and microstructural features were examined by scanning electron microscopy equipped with energy dispersive spectroscopy microanalysis system. The results showed that the major cause of the bare spots was the lack of wetability of the sheet surface due to contamination, improper heat treatment or chemical composition. Corrosion resistance was evaluated by standard salt spray test. Mechanical properties were examined by tensile testing. The time to red rust was much shorter on the bare spots as compared to other regions, but it appeared that bare spot defects had no significant effect on the mechanical properties of the galvanized steel sheets.

Galvanizing kettle is one of the main components of hot dip galvanizing process. Welding is the final stage in galvanizing kettle fabrication. In the present research the effect of various welding parameters such as bevel pattern and chemical composition of filler metal on mechanical properties, microstructure and corrosion resistance of welded galvanized steel were investigated. Results showed that symmetry bevel pattern is more effective than the non-symmetry one in developing desired properties in welding zone. Although both patterns developed acceptable mechanical properties in welded coupons. NDT results confirmed that welding zone is free from defects such as porosity, inclusion trapping, lack of penetration and etc. Various tests on the electrode type showed Nilsil electrode is more effective than AMA 1531 and 2000 electrodes in producing sound joints. Corrosion tests showed that silicon is the most detrimental element on corrosion resistance of welded coupons.

In this study the effect of the amount of Nickel in melted Zn and the amount of Si in base metal (steel) and also the duration of immersion time have been studied on three alloyed steels (DIN 1.0012, DIN 1.0037 and DIN 1.0042). Some parameters of coated layers such as total thickness, the thickness of the layers, the uniformity of coated layer, the cohesion of layer and finally the resistance against corrosion has been investigated. For this study optical and scanning electron microscopy which was equipped by EDX system and also salt spray test have been used. By studying several galvanized coatings it is shown that the best uniformity, cohesion and corrosion properties can be achieved by making use of a liquid bath, with 0.1%Ni.

In this study, the mechanical properties and tribological behavior of galvanized and galvalume coatings produced by hot dip method have been evaluated and compared. In addition, due to the high application of these types of sheets at high temperatures, the effect of long-term thermal cycles on the properties of these sheets was studied. For this purpose, samples of carbon steel plate with galvanized coating and galvalume with the same thickness were prepared. Then, structural and surface morphology was studied by scanning electron microscope and Elemental analysis, phase composition and crystalline texture were determined by X-ray diffraction. The mechanical properties of the coatings were evaluated by using Vickers hardness test and tensile test. The tribological properties of the coatings were investigated by pins on the disk test. Laboratory findings showed that overall the strength of galvanized sheet are greater than the Galvalume sheet, while it has a relatively less long elongation. while Galvalume has a weaker abrasive behavior than galvanized. In the case of galvanized sheet heat up to 300 ° C, the iron penetration from the steel substrate to the surface of the coating occurs and it forms brittle intermetallic phases that have a negative effect on the galvanized abrasion behavior. In other side, oxide layers also form on the surface of the coating and due to a better abrasive behavior. By heating the galvalume sheet at temperatures up to 400 ° C, the surface of the cover is dark, and bulges appear on it which indicates the formation of intermetallic phases and the presence of oxide on the surface of the coating. According to the results of this research in applications that friction coefficient is important, it is not recommended to heat galvanized and galvalume coatings at temperatures, respectively, above 300 ° C and 400° C.