Integrated Coating Lines: From Sheet Metal to Finished Cookware

Within the contemporary cookware production ecosystem, the coating line represents a pivotal value-creation node, transcending mere aesthetic enhancement to deliver functional performance, substrate protection, and regulatory compliance. This automated continuum of surface engineering processes fundamentally determines product longevity, food-release characteristics, and consumer safety perceptions.

Prior to entering the coating line, metallic substrates undergo rigorous transformation sequences. Raw sheet metal—typicallyaustenitic stainless steel (AISI 304/316) or precipitation-hardened aluminum alloys—first experiences precision blanking via hydraulic shearing or fiber laser cutting systems. Subsequent stamping and deep-drawing operations, executed on progressive dies with 500-800 ton capacities, impart the fundamental vessel geometry. Critical to coating success is the immediate post-forming surface rectification: automated deburring machines eliminate micro-serrations from shear zones, while multi-stage polishing lines utilizing compound-laden sisal wheels achieve Ra 0.2-0.4 μm surface roughness, optimizing mechanical interlocking for subsequent coating deposition.

The line initiates with a cascade pretreatment tunnel, where substrates encounter alkaline degreasing at 60-65°C using pH 12-13 solutions containing sodium metasilicate and non-ionic surfactants. This emulsifies drawing compounds and quenching oils inherent from forming operations. Dual-counterflow rinsing stages—with conductivity-controlled demineralized water at <50 μS/cm—neutralize residual alkalinity. For ferrous substrates, a zinc phosphate conversion coating (2-3 g/m² coating weight) generates crystalline phosphate dendrites, yielding superior corrosion resistance and priming adhesion. Non-ferrous alloys receive chromate-free titanium/zirconium passivation, ensuring environmental compliance while maintaining paint affinity