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Project Status: complete

Title: Effects of acid fog and dew on materials

Principal Investigator / Author(s): Mansfeld, F.

Contractor: Department of Materials Science and Engineering and Department of Civil Engineering, University of Southern California; CE Enviromental

Contract Number: A5-138-32

Topic Areas: Acid Deposition


Field exposure tests have been carried out in order to separate the effects of acidic fog on materials damage from those caused by rain, dew and natural weathering. The test sites were McKittrick and Visalia in the Central Valley and West Casitas Pass in Ventura County. These field tests have been supported by laboratory tests in which materials damage has been determined during exposure to carefully controlled fog water chemistry. The materials tested were galvanized steel, anodized aluminum, flat latex paint (on stainless steel) and high density linear polyethylene. At all three test sites and in the laboratory experiments atmospheric corrosion rate monitors (ACRM) were exposed which give a continuous record of the corrosion rates and the time-of-wetness of the sensor materials. Analysis of the field exposure results for galvanized steel and the paint samples shows that the corrosivity of the atmosphere at the three test sites must have been very low. This result is confirmed by the ACBM data which show very low corrosion activity. Since corrosion rates were so low approaching those for natural weathering, it was not possible to determine the effects of acidic fog. Based on the aerometric data and the observed corrosion behavior, it is doubtful that acidic fog conditions prevailed for significant times during the exposure period of 1/87-3/88 at Visalia and McKittrick. No damage could be determined for the anodized aluminum samples. Corrosion damage to polyethylene could not be detected by simple methods and is therefore not reported here. The results of the laboratory tests show that exposure to HN03 at low pH and to high pollutant concentration increased the corrosion rate of galvanized steel to over 10 m/year. Exposure to HN03 caused serious corrosion damage to anodized aluminum and the paint.


For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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