Per Olav Gartland

The role of ohmic potential drop in the initiation of crevice corrosion on alloy 625 in seawater

Abstract Analysis of the literature reveals that little attention has been paid to the role that IR , or ohmic potential, drop plays in initiating crevice corrosion. In the following paper experimental evidence supporting an IR -induced crevice corrosion mechanism for alloy 625 in seawater as presented and discussed. Depassivation of the metal within the crevice results when the IR drop down the crevice becomes large enough to force the crevice to reside at a potential where passivity is destroyed and active dissolution of the metal occurs.

The behaviour of corrosion-resistant steels in seawater: A review

Abstract Research on stainless steels in seawater carried out during the last decade is briefly reviewed. With natural seawater it is shown that the formation of a biofilm on the surface has an important influence on the local corrosion initiation tendency and propagation rate at temperatures up to 30–40°C. In chlorinated seawater the tendency to local corrosion initiation is even stronger, but the propagation rate is typically less than in natural seawater. Ageing of the surface is shown to have a distinct influence on the initiation tendency, and this observation may be utilized during the start-up of a chlorinated seawater handling system in order to minimize the risk of local corrosion. Finally, testing methods for corrosion in welds and crevices are briefly discussed and some typical results from such testing are shown. The critical corrosion initiation temperature and a lower critical repassivation temperature for crevices are dealt with.

Prediction of Galvanic Corrosion Rates and Distribution by Means of Calculation and Experimental Models

Abstract For numerical calculation of galvanic and total corrosion current densities on galvanic elements, the boundary element method has been used. Polarization curves have been determined experi...

Critical Crevice Temperature for High-Alloyed Stainless Steels in Chlorinated Seawater Applications

Eleven high-alloyed stainless steels (SS) were tested for application in chlorinated seawater. Critical crevice temperatures (CCT) were determined using a potentiostatic test method. Results were evaluated in terms of the critical crevice index (CCI) value of the alloys and compared to results of duplicate specimens in other tests.

EFFECTS OF FLOW ON THE CATHODIC PROTECTION OF A STEEL CYLINDER IN SEAWATER

Abstract The electric current density distribution around the circumference of a cathodically protected steel cylinder has been investigated. The water flow was perpendicular to the cylinder axis w...

Crevice Corrosion Repassivation Temperatures of Highly Alloyed Stainless Steels

An investigation was conducted to study the repassivation temperature of a highly alloyed austenitic (UNS S31254) and of a highly alloyed duplex (UNS S32750) stainless steel (SS). When initiated at a high temperature, repassivation occurred at a temperature level significantly lower than normally associated with initiation of crevice corrosion. Experimental results combined with computer modeling of crevice corrosion explored the mechanistic aspects. In this respect, the similarity between the hysteresis observed by cyclic polarization and cyclic temperature tests was emphasized.