Dust corrosion

Serious contamination formed on contact surface is one of the main reasons for electric contacts failure. Investigation shows that more than 60% of the corrosion products contain elements of dust, such as Si, Al, Mg, Na, Ca etc. Analysis for water solution of dust demonstrates that water-soluble salts are contained in the dust. Such solution forms electrolyte and makes metal corrosion. To illustrate the effect of dust on corrosion in real environment, elements of positive ions of dust, besides elements of corrosion products of Cu or Ni, have to be identified in the contaminants. Dust corrosion may cause connector contact failure within 2 months of operation. Long-term exposure in air shows that contact failure may be caused by both dust and gas corrosion. There seems to be no definite value of critical relative humidity (R.H.) for dust to corrode metal since corrosion can be found even R.H. value is as low as 10%. However, corrosion is increase rapidly with humidity. Corrosion can be greatly reduced by strictly controlling the humidity.