新しい省資源型ステンレス鋼（グリーンステンレス鋼）の開発に資するため，ステンレス鋼の不働態皮膜に関する研究を概説する．まず始めに実不働態皮膜の厚さと化学組成に関するその場分析の結果を述べ，次いで実不働態皮膜および理想ステンレス鋼を模擬した人工不働態皮膜およびイオンビームスパッタ蒸着Fe-Cr合金薄膜を用いたモデル実験によって得られたいくつかの重要な結果を述べる．最後に，硫化物介在物起点の孔食発生機構および鋼表面からの介在物除去による耐孔食性改善に関する最近の研究を紹介し，グリーンステンレス鋼が開発可能であることを示す．

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Ni-Cr-Mo系合金への少量Ta添加が耐すきま腐食性に及ぼす効果を定量的に評価するために，高温・高濃度塩化物環境である107℃ 25％NaCl中における腐食すきま再不動態化電位 (E_R,CREV) を測定した．その結果，Taは同じ添加量のCrやMoに比べて再不動態化電位を貴とする効果が大きいことが明らかとなった．また，Taを含有しない合金の耐すきま腐食性は，耐孔食指数であるPRE＝[％Cr]＋3.3([％Mo]＋0.5[％W]) と相関したが，Ta含有合金はその相関から乖離した．そこで，Ta含有合金の耐すきま腐食性を整理するために，PREにTa項を追加したPRE(Ta)＝[％Cr]＋3.3([％Mo]＋0.5[％W])＋7.7[％Ta]を提案した．

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Corrosion is one of the most important problems, particularly in relation to outdoor telecommunication equipment. Some corrosion prevention techniques such as crevice corrosion prevention for stainless steel and protective coatings on galvanized steel have been developed. As regards the latter, we have already developed a duplex protection system that employs resin coating and a galvanizing technique. There has been a need for weathering resistance technology that can protect telecommunications plant materials against damage during long-term use. In this work we have tried to improve the performance under various weathering conditions, in particular under ultraviolet (UV) light, which can easily damage polymer materials. Some powder paints designed to protect against UV light were prepared, and their performances were evaluated both with accelerated UV testing (e.g. with a xenon arc device) and when subjected to natural sunlight outdoor exposure in Okinawa, which has the most severe UV light conditions in Japan. We found that the UV absorber clearly improved the resistance to UV weathering. In addition, we tested for corrosion resistance under severely corrosive conditions outdoors at a coastal location on Miyakejima Island, and found that no blistering, cracking or corrosion occurred at current exposure time.

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