Progress in understanding of passivity and passivity breakdown on iron and iron-base stainless alloys for recent 20 years has been reviewed. Important experimental facts obtained on the structure, composition, and functions of passive films on the alloys were shown and novel mechanisms on the dissolution and passivation of iron was explained. Finally, future subjects that should be done for better understanding of the nature of passive films were proposed.
New novel techniques for surface characterization on an atomic level have been developed rapidly during past two decades. These techniques have been applied to corrosion research and provided great advances in corrosion science. In this article, their application results in corrosion science were reviewed focusing on scanning probe microscopic techniques such as Kelvin microprobe, scanning electrochemical microscopy, and scanning tunnel microscopy. Moreover, it was emphasized that quartz crystal microbalance gave the great contribution to study on minute corrosion of metal thin films.
Recent advances in corrosion protection of social infrastructures and buildings have been reviewed and future prospects are assessed, paying special attention to steel bridges, port facilities, and steel-structure houses and buildings including utility piping. The subjects covered are the increasing use of unpainted weathering steel for bridges, new introduction of weathering steel for coastal use, common adoption of heavy-duty coating systems for major long-span bridges over straits or in bay areas, widespread application of various linings for marine piles, expanding use of galvanized large structural members for steel-structure buildings, recent use of galvanized steel channels for steel-framed housing, and current corrosion protection of utility piping. In view of the growing demand for extended service life of infrastructures and buildings to cope with the labor shortage caused by the aging of society and to promote protection of the environment and conservation of energies and resources, the importance of corrosion engineering is emphasized.
Many kinds of stainless steels were developed for the usage in each industrial field. The research and development on stainless steel in these 30 years were described. A new refining process of stainless steel made it possible to reduce an impurity element to extra low contents, and to develop new stainless steels, e. g., many kinds of ferritic stainless steels. Furthermore, many of these stainless steels were standardized to the Japanese Industrial Standard. Super stainless steel with high corrosion resistance was developed as a roof material at a seaside area. New ferritic stainless steels with high thermal fatigue resistance were adopted to an automobile as an exhaust manifold. The suitable alloys from 13Cr stainless steel to high-alloyed steel were developed for tubings of oil and gas wells where the corrosion resistance largely depends on the contents of CO2 and/or H2S. Many corrosion problems occurred in a commercial nuclear power plant. The new corrosion phenomena were studied and elucidated by many researchers.
This report reviews recent progress in the research and development of corrosion protection technologies for nonferrous materials such as titanium, nickel, copper, and aluminum. Crevice corrosion resistant titanium alloys AKOT, TICOREX and SMI-ACE were newly developed which provide competitive low cost and almost the same corrosion resistance as Ti-0.15Pd. Hastelloy C-22, Hastelloy G-30, Inconel 690, and MAT21 were also developed which possess much more excellent corrosion resistance compared to the existing nickel alloys. Copper tubes in hot water supply system encountered pitting corrosion and copper alloy condenser and heat exchanger tubes in sea water erosion-corrosion, etc. and their countermeasures are described. Painted aluminum alloy sheets for automobiles suffered from filiform corrosion, and it could be prevented through alloy design, zinc-phosphate treatment, and/or zinc plating. In automotive heat exchangers such as radiator, heater, condenser, evaporator, etc. made from aluminum alloys, de-icing salt splash, engine coolant water, and/or condensate solution have been their severe corrosives, and their countermeasures are explained.
Material problems in oil-related facilities, that is, oil & gas wells, refineries and chemical process industries, were summarized for the last thirty years. Especially, in refineries, most of the material failures have been experienced and many research works to prevent the failures have been reported up to this time. However, many fire accidents due to corrosion failures have still occurred. As many large-sized plants in refinery and petrochemical complex in Japan have been operating for more than twenty years, newly developed reliable and economical maintenance technologies will be strongly requested.
Recent Trends in inhibitors are reviewed from the viewpoint of comparing inhibitor costs estimated by the Uhlig method in 1997 with that in 1995. The increase of inhibitor costs in boiler water and industrial cooling water is almost equal to the growth of Gross National Product (GNP). On the other hand, the cost of water treatment for air conditioning goes right on increasing. In the last three decades two main developments in inhibitor technologies had been accomplished. One is less toxic corrosion inhibitors such like phosphonates, zinc, polymers and natural materials instead of chromate and hydrazine. Another is polymeric dispersants for increasing the reuse of water. The demand for environmentally friendly corrosion and scale inhibitors, so called green inhibitors will accelerate the development of inhibitors that are more environmentally acceptable and cost-effective. Non-chemical water treatment combined with several processes such like deaeration, filtration, ion-exchange, reverse osmosis and so on will be also developed at the next decade.