Local corrosion dissolution of steel in earth-simulating solutions

Methods of optical in situ microscopy and scanning reflectometry were used to determine that localized corrosion defects (pitting) emerging on a pipe steel in a neutral solution simulate a neutral underfilm solution. The initial stages of this process were studied. The density, mean radius,and dimensions of corrosion spots (or pits) were determined. It was shown that the defects grew mainly into a depth that exceeded 100 μm after several hours and attained 600 μm after 33 days of corrosion tests. Similar behavior may lead to corrosion cracking under the cyclic mechanical stresses. The stress intensity factors realizable in steel in the event of localized corrosion defects were calculated, and the possibility of determining the danger of corrosion cracking initiation under stress of pipe steel was determined on the basis of both optical and electrochemical data.