製紙工場排出粉じんによる屋根瓦の腐蝕とその機構に関する基礎科学的研究(第1報)

Abstract

It had happened several decades gao in Kasugai city (Aichi prefecture) that roof-tiles (particularly, of smoking finish type) of the houses in the vicinity of a paper-mill corroded perceptibly; this episode made itself a nuisance to become the target of criticism. Thus, various studies had been started in 1964 and carried on till recently. The outline of the present report is as follows : It was found by chemical analysis that the corroded tiles contain Na_2SO_4 in an amount much larger compared to those of NaCl, Na_2CO_3 and others, suggesting such a corrosion mechanism that dust (say, of Na_2SO_4) emitted by the mill might fall upon tiles, penetrate into them if dissolved in rain-water and, in times, could crystallize there, displaying a destructive action against tiles. Another study had also been in progress : three huts of tiled roof were built within 1.5km at the farthest around the mill and allowed to stand idle for 12 years. The results so obtained is that the tiles near the mill got rich in Na_2SO_4,whereas those 1.5km distant suffered no change. Based on these findings, we have derived the equations (9) and (10) relating the Na^+ and SO_4^<2-> contents of a tile to the amount of dust falling onto it throughout the period of standing.