No Negative Impact on Initial Mechanical Properties
The patina is a thin (10–30 μm) oxide layer on the steel surface, which is too thin to change the internal microstructure or load-bearing capacity of the steel plate. The mechanical properties of S355J2W (yield strength ≥355 MPa, tensile strength 470–630 MPa, impact toughness ≥27 J at -20°C) are determined by its internal alloy composition and rolling process, not the surface patina.
Indirect Protection of Long-Term Mechanical Properties
The self-healing patina acts as a protective barrier that slows down the rate of substrate corrosion (to 1/4–1/10 that of ordinary carbon steel). Without this patina, the steel substrate would gradually corrode, leading to a reduction in cross-sectional area and a decline in load-bearing capacity over time. The self-healing function ensures the protective layer remains intact, preventing this long-term mechanical property degradation.
Minor Impact on Surface Hardness Only
The patina itself has a slightly higher hardness than the steel substrate, but this only affects the surface wear resistance (improves it slightly) and does not change the overall mechanical performance of the steel plate.
