This paper reviews electrochemical and corrosion studies on the application of carbon steel to an overpack container, which is used for the geological disposal of radioactive wastes. Deaerated alkaline Na2SO4-NaHCO3-NaCl solutions and bentonite soaked with the solutions are used as simulated geological disposal environments. Electrochemical studies show the corrosion of the steel in an early stage is the activation control. Corrosion rates are controlled by the composition of the solutions, alloying elements, and the structure of the steel. The rates decrease with time due to the formation of FeCO3 (siderite) film on the steel. Immersion corrosion tests show general corrosion morphology. Average corrosion rates of long duration have been evaluated. Clear proofs of the initiation of localized corrosion, such as pitting, crevice corrosion, hydrogen embrittlment and stress-corrosion cracking, have not been reported.
Creviced bent beam test is conducted on grain boundary character distribution (GBCD) controlled austenitic stainless steel. Average length and grain quantity of stress corrosion cracking (SCC) decrease after raising low Σ coincidence site lattice (CSL) grain boundary (GB) frequency by post-cold-work heat treatment process. GBCD analysis on SCC path shows that low Σ CSL GB possesses better SCC resistance than random GB. Triple junction distribution (TJD) analysis shows that with raising low Σ CSL GB frequency, continuity of random GB network can be efficiently broken, which leads to a good improvement of SCC resistance in the material.
Many telecommunication facilities are protected against long-term weather exposure by some type of weathering prevention technology. The steel poles used by radio stations are coated with polymer material to ensure both a long lifetime and reliability. Our goal is to develop a new technique for measuring the adhesive performance of a polymer film coating on galvanized steel by using a rheological approach. Conventional adhesion testing has proved difficult to reproduce, thus limiting its usefulness. In this study, we investigated the dynamic behavior of the polymer film, tried to evaluate the adhesive performance, and estimate the trend of the mechanical properties. Additionally, we have tried to correlate data obtained in a conventional way with data obtained with the rheological technique to predict the mechanical properties over the lifetime of the material. The result clearly shows the large time dependence of the mechanical properties. Continued film degradation during artificial accelerated cycle testing reveals the corresponding trend for dynamic storage and the loss modulus. We also found that it is possible to predict the potential breaking locations and the degree of strength of polymer films by comparing the results of conventional adhesive performance testing and our new rheological findings.