1. Intrinsic Atmospheric Corrosion Resistance Remains Fully Intact
Cold rolling is a room-temperature physical deformation process that only causes grain distortion and work hardening of the steel. It does not alter the core Cu/Cr/P weathering alloy composition of SPA-H, nor the content and distribution of corrosion-resistant precipitates in the matrix. Cold-rolled SPA-H forms the same dense and stable protective patina as hot-rolled SPA-H, with an identical long-term atmospheric corrosion rate of 0.01–0.03 mm/year.
2. Smooth Surface Improves Uniformity of Initial Patina Formation
The cold rolling process removes the rough mill scale and oxide layer on the surface of hot-rolled SPA-H, resulting in a smooth, flat and defect-free surface. This avoids localized uneven oxidation caused by surface defects in the early stage of outdoor exposure, ensuring the protective patina nucleates and grows evenly on the entire steel surface.
3. No Additional Localized Corrosion Risks Are Introduced
Work hardening and internal residual stress generated during cold rolling do not change the electrochemical properties of the SPA-H steel matrix. In normal atmospheric and mild coastal environments, the process will not induce sensitive localized corrosion such as intergranular corrosion, pitting corrosion or crevice corrosion.
4. Minor Edge Corrosion Potential Is Easily Mitigated
The only slight corrosion risk comes from the sharp cutting edges of cold-rolled plates, which may become temporary micro-corrosion initiation points due to stress concentration. This risk can be completely eliminated by simple post-processing such as edge grinding, chamfering or deburring, and will not affect the overall corrosion resistance of the steel plate.
