Anyị na-emepụta ngwaahịa dị iche iche nke corten steel nke dị mfe ịwụnye, mara mma nke ọma, na-eyi na ọnụ ala. Ma ịchọrọ ịmepụta mpaghara ahịhịa doro anya, kwụ ọtọ nke dị mfe idowe, ma ọ bụ usoro akwa ifuru nwere agba agba, ị nwere ike ime nke a ngwa ngwa, dị mfe na ọnụ ala site na iji AHL si n'okpuru ala na n'elu-ala corten nchara ogige n'akụkụ ngwọta.
N'afọ ndị 1930, US Steel rụpụtara ihe eji eme ihe n'èzí nke na-achọghị agba. Aha ya bụ Corten steel. Ogige akụkụ nke sitere na ígwè alloy yiri ya bụ akụkụ dị mkpa nke ngwaahịa anyị. Emebere nchara ahụ iji nweta patina mara mma n'ime obere oge, nchara a dị n'elu nwere ike ichekwa nchara ahụ pụọ na mmebi ọzọ. N'iji mkpụbelata nchara anyị nwere ihu igwe, ị nwere ike ịmepụta akwa ifuru mara mma, mpaghara ahịhịa, ụzọ ubi na osisi gbara ya gburugburu na-anwale oge. All nke anyị weathered ubi n'ọnụ na-abịa na a 10-afọ akwụkwọ ikike, ma na a obere mmezi na nlebara anya, ọ kwesịrị ịnọgide na ezi ọnọdụ ruo ogologo oge karịa nke ahụ: ma eleghị anya, 30 ma ọ bụ 40 afọ!