SPA-C is a typical weathering steel defined by JIS G 3125 that promote the formation of a dense, adherent oxide layer instead of loose, flaking rust.
In normal outdoor environments - including rural, urban, mild industrial, and low‑salt coastal atmospheres - SPA-C gradually develops a 1 to 3 years.
, effectively blocking the penetration of moisture, oxygen, and mild corrosive pollutants, thus preventing further deep corrosion of the steel substrate.
through re‑oxidation in the air.
Long‑term structural stability and appearance consistency can be maintained without painting, which is one of the typical characteristics of SPA-C in outdoor applications.
in harsh environments such as heavy salt spray, high sulfur dioxide pollution, long‑term water immersion, or poor ventilation, which may result in uneven, loose, or poorly adhesive rust.
