Fundamental Investigations on the High-Temperature Corrosion of Spinel-Forming Alumina Castables by Steel Slags

This study investigated the effect of the CaO/SiO2 mass ratio of steel slag on the corrosion behavior of spinel-forming alumina-based castables with a content of MgO (3–7 wt.%). Equiweight mixtures of castables and slags were calculated by FactSage, observed by HMTA, fired at 1350 °C, and investigated by XRD. From these results, we conclude that the presence of SiO2-rich phases accelerates the growth of the liquid phase in a narrow temperature range for the tested samples, which accelerates the degradation of castables. The static corrosion test was conducted by means of the coating method at 1450 °C. The corrosion index (IC) in the regions of castables affected by slags was calculated. Phases and phase distributions were evaluated by SEM-EDS. From these results, we conclude that for the slag with the lowest mass ratio of CaO/SiO2 (1.1), the reaction zone occurs only below the slag-refractory interface, which indicates the aggressive character of this slag.

The Effect of the Formation of Superelastic NiTi Phase on Static and Dynamic Corrosion Performance of Ni-P Coating

The addition of superelastic NiTi particles is a great benefit to the toughness of the Ni-P coating. Nonetheless, NiTi nanopowder costs 10 times more than Ti nanopowder. Therefore, in the present study, to reduce the cost, Ni-P-NiTi composite coatings were prepared on AISI 1018 steel substrates by the electroless incorporation of Ti nanoparticles into Ni-P followed by the annealing of Ni-P-Ti coatings. The effect of the formation of a superelastic NiTi phase on static and dynamic corrosion performance was investigated. It was found that the annealed Ni-P-Ti coating (i.e., Ni-P-NiTi coating) has much higher static corrosion resistance than the as-deposited Ni-P coating. The dynamic corrosion rates in the absence of abrasive particles are 10 times higher than the static corrosion rates of the coatings. The dynamic corrosion rates in the presence of abrasive particles are one order of magnitude higher than the dynamic corrosion rates in the absence of abrasive particles. The formation of a superelastic NiTi phase considerably improved the static and dynamic corrosion performance of the Ni-P coating. In the absence of abrasive particles under flowing condition, the dynamic corrosion resistance of the annealed Ni-P-Ti coating (i.e., Ni-P-NiTi coating) is 19 times higher than that of the as-deposited Ni-P coating. In the most aggressive environment (in the presence of abrasive particles), the dynamic corrosion resistance of the annealed Ni-P-Ti coating (i.e., Ni-P-NiTi coating) is four times higher than that of the as-deposited Ni-P coating. The annealed Ni-P-Ti coating (i.e., Ni-P-NiTi coating) can be used in applications where high corrosion resistance is required, especially in an extremely aggressive environment.

CORROSION-BEHAVIOR ANALYSIS OF A Fe-Al LAYER IN SEAWATER CHARACTERIZED BY STATIC CHEMICAL ETCHING

The static corrosion behavior of a Fe-Al layer was investigated with an immersion test in seawater, using XRD and SEM with EDS, testing the corrosion rate. The results showed that phases -Al2O3, Fe2O3 and MgO were the main corrosion products on the Fe-Al layer surface, while corrosion pits and holes were also observed. It was found that the Fe-Al layer fabricated at 750 °C exhibits a better corrosion resistance, having smaller corrosion pits and holes and also a low corrosion rate. This was related to a good formation ability of the alumina passive film.

Design, fabrication, testing and operation of a simulation facility for high temperature molten salt studies

Purpose Concentrated solar power and molten salt reactors use molten salts for heat energy storage and transfer. FLiNaK salts are being proposed to be used in these plants. However, structural material compatibility is the main hurdle for using molten salt in these systems. Hence, it is essential to study the degradation of materials in high temperature molten FLiNaK salt environment. In view of this paper aims to describe, a simulation facility which was established and operated for carrying out high temperature static corrosion studies of materials under molten FLiNaK salt. Design/methodology/approach This paper describes about the design criteria, method of designing using ASME codes, material selection, fabrication, testing, commissioning and operation. Also, a few experimental results have been illustrated. Findings A simulation facility could be designed, fabricated, commissioned and is being successfully operated to carry out corrosion experiments under static molten FLiNaK environment. Research limitations/implications The facility has been designed for 800°C and maximum temperature of experiment would be restricted to 750°C. The materials tested in this facility can be validated only up to 750°C temperature. A maximum of four exposure periods can be studied at a time with around ten specimens for each exposure. Originality/value Selection of compatible material for the facility and design certain unique features like extracting exposed specimens of intermediate periods without actually shutting down the autoclave and measuring the level of molten salt at high temperature.

g EFFECT OF VIBRATION-CORROSION ON ALUMINUM ALLOY(DIN1100) THAT WELDED BY TIG TECHNIQUE AND OPERATING IN THE MARINE ENVIRONMENT

In this research studied the effect of corrosion in presence of vibration on aluminum alloy type (DIN1100) operating in sea water (3.5% NaCl) and compared these results with the same alloy after it was welded by TIG technique at the same vibrated corrosive medium, addition to study the corrosion in static medium for welded and non- welded alloy, then comparison between the four cases depending on corrosion rates and microstructures it was noted that ;the greatest percentage of corrosion rate was 43% of welded alloy at vibration-corrosion and least percentage of corrosion rate was 8% of non-welded alloy at static corrosion.

Static corrosion tests of iron-based biomaterials in the environment of simulated body fluids

Biodegradable metallic implants are materials that serve as a temporary implants and scaffolds. They degrade directly in vivo and therefore eliminate need for secondary surgical intervention. They are often made of metals such as magnesium, iron, zinc and can be modified by coating with the inorganic or polymeric layer. In this work iron-based biomaterial was prepared and modified with polymeric (polyethyleneimine, PEI) layer. Its degradation behavior was studied under conditions of simulated body fluids at 37 ± 0.2 °C in the form of static immersion tests. It has been shown that the surface modification caused an acceleration of degradation of the material and also had an influence on the corrosion mechanism.

Carbon-14 release and speciation from carbon steel in highly alkaline conditions

ABSTRACTThe release and the speciation of carbon species from irradiated JRQ carbon steel samples, representative of the reactor pressure vessel of Belgian nuclear power plants, were studied in a saturated portlandite aqueous solution, relevant for the Belgian Supercontainer design, as perceived for the geological disposal of high-level nuclear waste. To achieve this, we performed simple immersion and potentiostatic corrosion tests. In addition, the corrosion rate (which determines the 14C release) was estimated by measuring the release of 60Co. Gas chromatography showed that during the static corrosion test, the carbonaceous species methane, carbon dioxide, ethene, and ethane were produced. Under the hypothesis that all the carbon released from the JRQ steel was transformed into carbon-base gaseous compounds, this corresponds to a corrosion rate of approximately 100 nm/yr, which is in good agreement with literature data.