Color stability control of stainless steel color plate: optical mechanism from oxide film structure to nano photonic crystal

Keywords: stainless steel color plate, color stability, nanophotonic crystal

Summary:

The color stability of stainless steel color plates is significantly affected by the structure of the oxide film, environmental factors, and photoaging. This article combines XRD, SEM, and spectral analysis to reveal the relationship between the grain size, porosity, and color of the oxide film. A synergistic control scheme of nano photonic crystal structure and self-healing coating is proposed to achieve a color difference Δ E<1.5 (GB/T 11186.3) for the color plate after 5 years of outdoor exposure.

Core content:

The relationship between oxide film structure and color:

Grain size effect: When the grain size of Cr ₂ O Ⅲ in the chemical oxide film increases from 20nm to 100nm, the interference color shifts from golden (λ=580nm) to deep red (λ=650nm);

Porosity regulation: By adding nano SiO ₂ (particle size 20nm) to seal the pores of the oxide film, the porosity is reduced from 18% to 5%, and the UV aging resistance time is extended from 200 hours to 1000 hours;

Phase composition analysis: XRD results show that a dual phase structure of Cr ₂ O Ⅲ and FeCr ₂ O ₄ is formed in the oxide film of Mo containing stainless steel, and the color saturation is increased by 40% compared to the single-phase film.

Nano photonic crystal regulation:

Colloidal crystal template method: Self assemble SiO ₂ microspheres (diameter 220nm) on the surface of stainless steel, fill Ni by electrodeposition to form a reverse opal structure, with a reflection peak full width at half maximum<30nm and a color purity of 95%;

Plasmon resonance enhancement: On the surface of an oxide film modified with Au nanoparticles (diameter 10nm), local surface plasmon resonance (LSPR) increases color brightness by 60% and reduces angle dependence;

Dynamic color control: By driving the orientation change of liquid crystal molecules through an electric field, the reflection wavelength can be continuously adjusted from 550nm (green) to 650nm (red), with a response time of less than 100ms.

Self repairing coating technology:

Microcapsule coated repair agent: Microcapsules (diameter 10 μ m) containing benzophenone (photoinitiator) are embedded in the epoxy coating, and the repair agent is released under UV irradiation to fill scratches, with a repair efficiency of>90%;

Supramolecular self-assembled membrane: Based on cup-shaped aromatic derivatives, self-assembled monolayers achieve automatic scratch repair through host guest interactions, with a contact angle restored to 110 ° and a repair life of up to 100 cycles;

Environmental adaptability: The self-healing coating can maintain its function in environments ranging from -40 ℃ to 80 ℃ and relative humidity of 5% -95%, extending its lifespan by 5 times compared to traditional coatings.

Accelerated aging experiment:

QUV test: After exposure to UVA-340 lamp (0.76W/m 2 @ 340nm) for 3000 hours, the color difference Δ E of the nanophotonic crystal color plate was 1.2, which was 70% lower than that of the chemical coloring plate;

Salt spray humidity cycle: after 500 hours of 5% NaCl spray+85 ℃/85% RH humid heat alternation, the corrosion area of self repairing coating color plate is less than 0.1%, and the retention rate of adhesion strength is more than 95%.

High end field applications:

Luxury watch case: stainless steel color plate with nano photonic crystal and self-healing coating, achieving 3 years of scratch free and zero color decay on Rolex watches;

Optical instrument housing: Dynamic color control technology is applied to the Zeiss microscope housing, which matches laboratory ambient light through current regulation to reduce visual fatigue.