Iwao Matsushima

Corrosion resistance of Al-based metal matrix composites

Abstract Corrosion characteristics of Al 6061-based metal matrix composites (MMCs) containing carbon fibres, alumina fibres or silicon carbide whiskers (SiCw) and the effects of ageing heat treatment on the stress corrosion cracking resistance of SiCwAl 7075 MMC were studied in chloride solutions. MMCs were prepared by the squeeze casting method in the laboratory. The pitting potentials for Al 6061 and the three Al 6061-based MMCs were similar. The resistance of SiCwAl 6061 MMC to pit initiation is the same as that of the monolithic alloy. Once pits initiate, damage by pitting corrosion would be greater owing to the formation of crevices between the reinforcement and the matrix by the dissolution of the latter in the pits. The cathodic current of the SiCwAl 6061 is slightly larger than that of the matrix alloy, possibly owing to an interfacial layer observed by transmission electron microscopy. Ageing of SiCwAl 7075 MMC at 170 °C for more than 1 h following ageing at 110 °C makes the MMC resistant to stress corrosion cracking in 3.5% NaCl and increases the pitting potential.

Polarization Behavior of High-Alloy OCTG in CO2 Environment as Affected by Chlorides and Sulfides

Abstract Pitting corrosion resistance of 13% Cr steel, duplex stainless steel, and high Ni austenitic stainless alloys for Oil Country Tubular Goods (OCTG) has been examined by electrochemical meas...

Corrosion Engineering of Social Infrastructures and Buildings-A Historical Review of Events of Past Half Century-

過去半世紀におけるわが国の社会資本構造物及び建築物の防食技術の発展を、社会の変化及びそれによって生じたニーズと関連付けて概説した. これは現在の防食技術の歴史的背景を新世代に伝承することを意図している. 短い歴史的概説に続いて, 10項目のトピックについてより詳細に述べた. 取り上げたのは, 無塗装耐候性鋼の利用, 初期における埋設パイプラインの電気防食, 鉄筋の腐食を避けるためのコンクリートの品質管理, 高力ボルトの遅れ破壊対策, 水配管に用いる耐みぞ状腐食電縫鋼管の開発, 建物周辺の埋設配管の早期腐食対策, 長大海上橋梁への重防食塗装系の適用, 海水飛沫帯防食のためのライニング, 『荒廃するアメリカ』 (P. Choate, S. Walter著) の衝撃的教訓, 及びアメニティのための建築物外装への耐さび性ステンレス鋼とチタンの使用である.

Critical Contents of Nickel and Chromium Required for SCC Resistance of High Alloy Oil Country Tubular Goods

Abstract Based on the laboratory SCC test results of 10 to 37% Cr, 25 to 45% Ni, 3% Mo, bal. Fe alloys, it is shown that the beneficial effect of increased Ni content on SCC resistance is retained only when the Cr content is appropriate. Good SCC resistance is obtained when the stability of austenite is above a critical value; therefore, the content of ferrite formers, e.g., Cr and Mo, should not exceed a certain limit determined by the content of austenite formers, e.g., Ni. The critical stability of austenite depends on the annealing temperature, a higher temperature requiring a higher stability of austenite.

A Basic Concept of Long-Term Corrosion Protection of Infrastructures

Critical issues to be solved were considered and a basic concept was proposed to establish effective corrosion protection of infrastructures that require increasingly long service life with a minimum of maintenance to conform to the aging of society and the avoidance of 3D (dirty, dangerous and demanding) jobs. An appropriate service life for each type of infrastructure must be set by the government from the standpoint of economy and the welfare of society rather than that of technological capability as is the case of 100 years life for long-span highway bridges in the bay areas. Future long-term corrosion engineering to meet the requirement must be the one most appropriate from the inclusive standpoint of total-life economy, labor saving and friendliness to the earth. Formulas to evaluate the total score are not available yet due primarily to the difficulty of judging relative size and importance of impact upon protection of the environment and conservation of energy and resources, and must be developed by the cooperation of technical societies of various areas including corrosioin engineering. Reliable life prediction of specific corrodible structures is a critical item in evaluating a corrosion protection system, which can basically be made by using compiled practical corrosion data with proper modifications with respect to structural, environmental and time factors.

Statistical characteristics of pit depth observed on inner surface of carbon steel pipes.

Statistical characteristics of pitting corrosion observed under tubacular on carbon steel used for fresh water pipes are discussed. Thirty three cases were analysed using the statistical method. The Gausian distribution was applied for the distribution of pit depth in carbon steel. The mean and standard deviation of pit depth had no dependence on duration of use in practice. The standard deviation of pit depth rather than the mean is a good indicator for the estimation of potential occurrence of penetration. The index, m+3σ, is a good indicator for the occurrence of perforation. The standard deviation and mean of pit depth showed good correlation. It is difficult to estimate the life time of pipes using statistical analysis of pit depth because the law of pit growth is unclear.