In the transmission industry, the use of weathering steel, also known as COR-TEN, began as early as 40 years ago. Many utilities prefer to use weathering steel because of its aesthetically pleasing brown, organic finish that helps poles to blend into wooded areas.
Weathering steel originally was believed to be low maintenance; it was advertised and sold as an install-and-forget-it material. However, this is not the case. Routine maintenance is required on lines located where dense vegetation may grow up around the bases of structures, holding moisture and preventing proper formation of the weathering patina. Although American Electric Power (AEP) successfully uses weathering-steel poles on its system, one of its 20-year-old pole lines was showing signs of severe corrosion the utility had to address.
Following are images of the issues AEP found. For the full, in-depth article, see "A Second Look at Weathering Steel."