SLXTEEN-YEAR ATMOSPHERIC CORRSION EXPOSURE STUDY OF STEELS

Sixteen-year atmospheric exposures of 17 steels at 7 sites were made.Power function D=Atn can describe the corrosion process quite well.The pattern of corrosion development in the early stage is different from that in the long-term exposure.It is not proper to determine corrosivity of an environment by means of one-year exposure result,a method stipulated by ISO-9226.It is also not correct to predict the long-term corrosion results by short-term exposure.The major damaging pollution factors are sulphur dioxide and chloride ion.The effect of sulphur dioxide is serious in the early exposure years.It is no longer so in the later years.Environment factor of humid hot is much more important in long run.In addition of chloride ion pollution,an extradinary high corrosion can be resulted in mild steels.