A SEM/EDXA study on the chemical attack of aqueous NaOH/KOH solutions on the surface of the metal-metalloid glass (Fe, Cr)80 (P, C, Si)20 and Fe75Cr5P8C10Si2, respectively

Abstract

Abstract. After a treatment of the metal-metalloid glassy alloy (Fe, Cr)80 (P, C, Si)ao and Fe75CrsPsCloSi2, respectively, by aqueous alkaline solutions of 1.0M NaOH+I.0M KOH and 2.5M NaOH + 2.5 M KOH, respectively, a SEM/EDXA study of the glass surface was performed.The results of the accelerated ageing procedure demonstrate that the glass treated with the 1.0 M NaOH + 1.0 M KOH solution at room temperature (20 ~ is characterized by a surface state like that of the initial material.For the glass treatment with the 2.5 M NaOH + 2.5 M KOH solution at 20 ~ the surface layer shows a different morphology and is thicker. It can be supposed that the reinforcing property is reduced.The glass treatment at 80 ~ with the aqueous solutions 1.0 M and 2.5 M (NaOH + KOH), respectively, leads to surface layers of different morphology and such a layer is about 5 ~tm thick. The strength of solid residue of such a treated glass is very low.Key words: scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDXA), metal-metalloid glassy alloy of chemical composition (Fe, Cr)s o (P, C, Si)2o, accelerated ageing procedure, aqueous alkaline environment of mixed NaOH + KOH.For a reinforced composite material with ribbons of the metal-metalloid glassy alloy (Fe, Cr)a o (P, C, Si)2 o and Fe75CrsPsC~oSi2, respectively, one can assume a larger time of application than that of the well-known asbestos cement products. Because there is no experience with the behaviour of this new material one must simulate processes with these reinforcing elements and use an accelerated ageing procedure to predict the * Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday ** To whom correspondence should be addressed properties of the ribbons in cementitious environments for 50 years and more.For such an inorganic composite material made with glass, "fibres" and ribbon, respectively, there is established the term glass fibre reinforced cement or concrete (GRC)-the reinforcing component is embedded in an ordinary Portland cement (OPC) or concrete matrix with an alkaline environment of a pH in the region of 13 to 14 caused by the chemical composition of the pore solution consisting of KOH, NaOH and saturated with Ca(OH)2. Differences in the alkaline concentration are mainly caused by the type of cement, the additives, aggregates and the degree of hydration process. Cement and concrete, respectively, which is reinforced with silicate glass fibres can show a specific material behaviour in dependence on the degree of durability of the silicate glass surface with the alkaline environment and so also break-downs occured with the so-called alkali resistant silicate glass fibres (ARG) for technical applications in the past time. But contrary to numerous investigations and publications concerning silicate glass fibres there exist only few scientific articles on the corrosion behaviour of this metal-metalloid glassy alloy. An orientation with this new material on comparable metals of a chemical composition like ...