Abstract
Crevice corrosion and pitting occur when chromium bearing stainless steels, chromium-nickel stainless steels and nicker are immersed in quiet sea water. The crevice corrosion on these materials is of the oxygen concentration cell type of attack. The pitting of these materials is usually severe in sea water. Monel in quiet sea water suffers slight, shallow pitting attack which usually is arrested before deep penetration occurs.
Experiments were conducted in sea water at Kure Beach, N. C, to determine the effectiveness of cathodic current in reducing these forms of corrosion. Test specimens were coupled to magnesium anodes with appropriate resistors in each circuit to control the currents. Potential measurements were made -during the course of two runs of four and six months, respectively.
Cathodic current in quiet sea water reduces pitting and crevice corrosion on Types 410 and 430 stainless steels but its use is impractical because it causes severe blistering when the current is sufficient to eliminate the corrosion. This blistering is due to hydrogen which is formed on the cathode surfaces by the current. Hydrogen is also generated on mild steel surfaces but does not ordinarily produce blistering:
Cathodic currents effectively reduced these forms of corrosion on nickel, Monel and Types 302 and 316 stainless steels without the development of blisters even at 30 ma per sq. ft.
