The technology of non-toxic corrosion inhibitors developed as a replacement of chromate in cooling water treatment was reviewed. Polyphosphate and phosphonate react with mother metal ion to form a protective film at anodic sites. On the other hand they form a protective film by precipitation with zinc ions and / or calcium ions at cathodic sites depending on their concentration. Acryl acid based polymer or maleic acid based polymer used as scale inhibitor enhances the effectiveness of cathodic inhibitors for carbon steel, and also made possible to increase the cycle number of concentration in cooling water and to decrease the total amount of phosphate in effluent water. The developments of green inhibitors, scale inhibitors for silica scale, non-chemical water treatment devices, and so on are expected in future.
In industrial boilers that use low-grade fuel, high-temperature sulfidation corrosion and vanadium attack have been major issues. High-temperature corrosion tests using actual boiler ash were performed for six heat-resistant cast alloys as candidate materials for burner chips and swirlers. At 850°C, corrosion was not sever, and SCH2 and 50Cr50Ni exhibited particularly good corrosion resistance. However, at 1050°C, corrosion weight loss of 50Cr50Ni, 30Cr70Ni, SCH13, and SCH22 dramatically increased, whereas that of 60Cr40Ni and Ni-less SCH2 was relatively small. Such corrosion mechanisms are discussed on the basis of microstructure observations and the results of EBSD and EDX analyses.
Samples of low-density polyethylene (LDPE) were photodegraded using accelerated weathering instruments and outdoor exposure. The physical properties and chemical structures of the photodegraded samples were studied through a tensile test, gel chromatography, and infrared spectroscopy. The molecular weight distribution of a photodegraded sample by using a fluorescent UV lamp at a high black panel temperature (80°C) was more similar to that of an outdoor-degraded sample than that of other artificially photodegraded samples by using a Xenon lamp at the standard black panel temperature (63°C). It is estimated that accelerated weathering tests at a high sample temperature could accelerate cross-linking than chain scission, consequently recreating molecule-enlargement similar to the outdoor-degraded sample.