Structural‑phase composition of a gas‑thermal coating of Fe‑Cr‑Ni‑Al pseudo alloy subjected to annealing

The structural‑phase state of the gas‑thermal coating made of Fe‑Cr‑Ni‑Al pseudo‑alloy in the initial state, as well as after annealing in the temperature range 550–650 °C for 20–60 minutes, has been investigated. It has been established that the phase composition of the Fe‑Cr‑Ni‑Al pseudo‑alloy in the initial state includes mainly Al and α‑Fe, and its porosity does not exceed 3–5 vol.%. Annealing of a thermal spray coating from a pseudo‑alloy at temperatures of 550–650˚C for 20–60 minutes leads to the release of iron‑aluminum intermetallic compounds Fe3Al, Al13Fe4 and Al5Fe2, an increase in hardness and porosity.

Role of Coating Processes on the Corrosion Kinetics and Mechanism of Zinc in Artificial Seawater

Zinc (Zn) coating is being used to protect steel structures from corrosion. There are different processes to deposit the coating onto a steel substrate. Therefore, in the present study, a 100 µm thick Zn coating was deposited by arc and plasma arc thermal spray coating processes, and the corrosion resistance performance was evaluated in artificial seawater. Scanning electron microscopy (SEM) results showed that the arc thermal spray coating exhibited splats and inflight particles, whereas plasma arc spraying showed a uniform and dense morphology. When the exposure periods were extended up to 23 d, the corrosion resistance of the arc as well as the plasma arc thermal spray coating increased considerably. This is attributed to the blocking characteristics of the defects by the stable hydrozincite (Zn5(OH)6(CO3)2).

Mitigating CO2 Corrosion of Natural Gas Steel Pipelines by Thermal Spray Aluminum Coatings

Internal pipeline corrosion due to CO2 is a major challenge facing the oil and gas industry. To protect the pipelines and equipment from the ravages of CO2 corrosion, novel sacrificial coatings can be used. The objective of this study was to investigate the corrosion behavior of Al-based alloys as sacrificial coatings to protect pipelines in a CO2-saturated aqueous electrolyte (3.5 wt.% NaCl) at 4 bar CO2 partial pressure (3 barg) and 40 oC. The corrosion resistance of Al-based alloys and thermal spray coatings was evaluated in an electrochemical reaction autoclave using electrochemical methods (potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy). Post-corrosion surface characterization was performed by scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The obtained data show Al-based alloys demonstrated promising protection against CO2 corrosion with no breakaway degradation issues.

Manufacturing and performance evaluation of medical radiation shielding fiber with plasma thermal spray coating technology

Lead, which has been used for radiation shielding in medicine, is currently sought to be replaced by an eco-friendly shielding material. Therefore, it should be replaced with shielding materials possessing excellent processability and radiation shielding performance similar to that of lead. In this study, a new process technology was developed focusing on the processability of tungsten, a representative eco-friendly shielding material. It is difficult to reproduce the shielding performance when using the method of coating nonwoven fabrics with a liquid using tungsten powder on a polymer material, which is adopted to ensure the flexibility of the shielding fabric. To address this, tungsten powder was sprayed on the fabric using a plasma thermal spray coating process and coated to a thickness of 0.2 mm to evaluate the shielding performance. Compared to standard lead with a thickness of 0.2 mm, the shielding efficiency differed by approximately 15%. Since the developed process can maintain the amount of injection in an area, it is possible to ensure the reproducibility of the shielding performance and automated process for mass production. This approach is economically feasible as it does not entail the mixing of polymer materials; hence, it can be used for preparing radiation shielding clothing for medical institutions.