A commercial complex curtain wall in a coastal city originally used 304 brushed panels, and within one year of delivery, rust spots and color-difference complaints appeared.

Causes: chloride deposition from the marine atmosphere + surface iron contamination + color differences between batches.

Optimization plan: - Upgrade the material to 316L, with panel thickness calculated according to wind pressure (1.5-3.0 mm). - Unify the brushed direction on the surface, produce from the same batch, and seal samples. - Pickle and passivate after processing, and apply protective film for transport. - Establish a cleaning and maintenance regime every six months.

Conclusion: Coastal curtain walls should use 316L by default, and "passivation + maintenance" should be written into the contract annex.