Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Surfaces and Interfaces  

This study investigated the corrosion resistance and durability of Al-5Mg coatings deposited by transferred arc plasma spraying (TAPS) and flame spraying (FS) methods. The corrosion performance was evaluated through a 6000-hour accelerated corrosion test, complemented by electrochemical impedance spectroscopy and polarization measurements. The TAPS coating exhibited significantly lower initial porosity of 3.78%, reducing further to 1.09% after 1000 corrosion cycles, compared to the FS coating with an initial porosity of 9.93%, decreasing to 5.46%. Electrochemical tests revealed a lower corrosion current density in the TAPS coating (1.90 μA/cm²) than in the FS coating (2.54 μA/cm²) after 1000 cycles, indicating a superior corrosion resistance of the TAPS coating. Additionally, adhesion strength measurements indicated that the TAPS coating exhibited approximately 20% higher adhesion strength compared to the FS coating, further enhancing its durability and mechanical reliability. The enhanced performance of TAPS is attributed primarily to its dense and uniform pore structure and the resultant formation of a compact, protective oxide passive layer, effectively inhibiting electrolyte penetration. Overlay tests further confirmed that TAPS coatings exhibited significantly reduced blistering under linear defect conditions. These findings suggest that the TAPS process is a highly effective method for enhancing the corrosion protection of Al-5Mg coatings on complex steel structures.

DOI： 10.1016/j.surfin.2025.106377

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Progress in Organic Coatings  

The effects of abrasive water-jet treatment (AWT) on the deformation of carbon steel surfaces and the adhesion of epoxy adhesives were analyzed. Different abrasive sizes and standoff distances were considered to evaluate the changes in surface properties of carbon steel produced during the AWT process in terms of surface roughness, surface topography, and residual abrasive distribution. Compared to conventional abrasive blasting, the AWT processing provided higher surface roughness and surface deformation ratio (DR), and significantly lower residual abrasives amount. Notably, the study found a tendency for adhesion to decrease with increasing surface roughness. This is in contrast to the conventional literature, which suggests that adhesion to paints and adhesives improves with increasing surface roughness up to a certain threshold level. On the other hand, DR showed a strong positive correlation with adhesion, but above a certain value, adhesion tended to be lower than that of the blast treatment. The findings indicate that it is preferable to consider both conventional surface roughness and DR concurrently when assessing adhesion. This study will contribute to a deeper understanding of the influence of surface properties during AWT on the adhesion performance of epoxy adhesives and suggest optimal surface treatment conditions for practical engineering applications.

DOI： 10.1016/j.porgcoat.2025.109137

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Progress in Organic Coatings  

Thermal spray coatings, such as Zn, Zn-15Al, Al, and Al-5Mg, combined with heavy-duty paint, are increasingly used to enhance the corrosion resistance of steel structures. However, the overlaid areas of these coatings, particularly in damaged regions, can become weak points for corrosion initiation. To investigate the deterioration mechanisms at the overlaid zones of heavy-duty paint and thermal spray coatings on carbon steel plates, this study designed atmospheric exposure experiments and employed 3D scanning, electrochemical testing, and scanning electron microscope (SEM) - energy-dispersive X-ray spectrometer (EDX) analysis to systematically assess the degradation of the overlaid coatings in marine atmospheric environments. The results indicate that electrochemical reactions at coating defects drive the blistering and delamination of the overlaid coatings. Zn-based coatings, which provide sacrificial protection, exhibit slower failure progression compared to Al-based coatings, which show blistering due to passivation film formation. These findings provide valuable insights for optimizing thermal spray selection and overlaid coating strategies in marine atmospheric environments.

DOI： 10.1016/j.porgcoat.2025.109057

Web of Science

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：Corrosion Science  

The surface texture of 144 weathering steel samples were analyzed under marine atmospheres to assess the effects of the exposure conditions and structural factors. Comprehensive methods were used to characterize the corrosion evolution and pitting performance. Geospatial variability was introduced as a new method for quantifying non-uniform and irregular surface substrates. The results showed significant variations in corrosion severity under identical environmental conditions. Closely spaced pits formed clustered patterns with an increased range, whereas isolated sparse pits demonstrated the converse. Sill effectively captured serrated surface variations. Explainable machine learning models were developed to regenerate and predict the steel surface texture.

DOI： 10.1016/j.corsci.2024.112602

Web of Science

Scopus

Language：Japanese   Publisher：Journal of Building Engineering  

The effects of a newly developed nozzle type, with divergent flow, and abrasive particle size on the surface preparation properties of steel substrate using abrasive water-jet treatment (AWT) were analyzed. The corrosion and chloride removal efficiencies were evaluated by applying this technique to parts of severely corroded steel structures. The evaluation of the surface characteristics of the treated specimens included analysis of the treatment area, maximum erosion depth, surface roughness profile, and residual abrasive material quantity. The corrosion removal efficiency was assessed using surface salinity measurements and SEM-EDX analysis. The experimental results demonstrated that the application of the developed divergent nozzle and smaller abrasive particle sizes in the AWT process resulted in an expanded treatment range and effective prevention of excessive erosion depth and surface roughness. Additionally, ultra-high-pressure water with abrasives completely eliminated corrosion products and chlorides present on both the surface and interiors of the corroded steel surface, achieving a cleanliness level exceeding Sa 3. This process prevented the formation of flash rust on the cleaned surface for up to 24 h and prolonged the time before the reoccurrence of corrosion on the treated surface. To summarize, the AWT with a divergent nozzle and smaller abrasive particles creates the most ideal surface preparation characteristics for subsequent coating and provides higher surface cleanliness suitable for practical engineering applications.

DOI： 10.1016/j.jobe.2024.108623

Web of Science

Scopus