1. Chemical Accelerated Patina Treatment (Most Widely Used)
Process Steps
Surface Preparation: First, remove oxide scales, rust, and contaminants from the steel plate using shot blasting or high-pressure water jet cleaning (avoid acid pickling, which can over-etch the surface). Ensure the surface is dry and free of grease.
Solution Application: Apply a weathering steel patina accelerator (composed of ferric chloride, copper sulfate, and a small amount of hydrochloric acid, or commercial ready-to-use formulas) evenly to the surface via spraying or brushing. The solution concentration is typically 5–10% to avoid excessive corrosion.
Humidity & Temperature Control: Place the steel plate in a high-humidity environment (relative humidity 70–90%) at 20–30°C. Mist the surface with fresh water 1–2 times daily to maintain moisture-this promotes the formation of a dense iron oxide layer with alloy enrichment.
Curing: After 7–14 days, a uniform reddish-brown patina will form. Rinse the surface with clean water to remove residual chemicals, then let it air dry naturally.
2. Thermal Accelerated Patina Treatment
Process Steps
Clean the steel surface thoroughly to remove impurities.
Heat the steel plate to 300–400°C in a furnace with controlled humidity (introduce water vapor to simulate outdoor moisture).
Hold the temperature for 2–4 hours, then cool the plate slowly in air. The heat accelerates the reaction between iron and oxygen, forming a uniform patina layer.
3. Post-Treatment for Accelerated Patina
Apply a transparent breathable sealant (e.g., acrylic-based or fluorocarbon sealant) after the patina forms. The sealant locks in the color without blocking air/moisture exchange, ensuring the patina retains its self-healing ability.
Avoid using non-breathable coatings (e.g., epoxy paint), which trap moisture under the film and cause localized corrosion.
