Mechanical Polishing & Deburring
This is the basic and essential pre-treatment step. Use 200–400 mesh sandpaper, abrasive wheels, or hand-held deburring tools to grind the sharp burrs, serrations, and micro-cracks left by cutting/welding. The goal is to smooth the edge surface until it is flush with the base material, eliminating stress concentration points and corrosion initiation sites. For thick-walled flower boxes (≥5mm), chamfer the edges to a 2–3mm angle to avoid sharp corners that are prone to collision damage and rust accumulation.
Passivation Treatment
Apply a weathering steel-specific passivation agent to the polished edges. The agent contains corrosion-inhibiting components that react with the fresh steel substrate to form a thin, stable oxide film, which speeds up the integration of the edge rust layer with the overall patina of the flower box. It also suppresses the rapid, uneven rusting of exposed steel in the early stage, avoiding loose rust powder or rust water seepage from edges.
Patina Accelerator Coating
For flower boxes that need consistent rust color, coat the treated edges with a dilute, non-toxic patina accelerator after polishing. The accelerator (usually containing iron ions and organic acids) promotes the formation of a dense, reddish-brown rust layer on the edges at the same rate as the main surface of the flower box, eliminating color differences between cut areas and pre-rusted surfaces. This method is especially suitable for pre-rusted flower boxes before installation.
Localized Transparent Glaze Sealing
For flower boxes used in harsh environments (coastal high-salt areas, industrial zones) or to prevent rust water from contaminating soil/plants, apply a thin layer of matte UV-resistant transparent glaze to the edges after the patina stabilizes. The glaze forms a protective barrier on the edge surface, enhancing corrosion resistance without covering the overall rust texture of the flower box. It also locks in loose rust particles to avoid staining.
Weld Seam Treatment (for welded flower box edges)
For edges formed by welding, first grind the weld seams flat with a grinding wheel to remove weld spatter and uneven protrusions, then polish with 400–600 mesh sandpaper to smooth the transition between the weld and the base material. After that, apply passivation agent or patina accelerator to the treated weld area to ensure the rust layer forms uniformly, preventing rust from accumulating in weld crevices.
