How to fight against galvanic coupling between buried and submerged side of a steel pile in seawater

摘要

Buried side of a steel pile in coastal environment is subject to galvanic coupling with the water side. Corrosion rate cannot be negligible and depends on steel surface and oxygen availability. Cathodic protection is the only solution to counteract this deleterious reaction. Cathodic protection of the buried part of the piles in the marine environment has not been studied or modelled in detail to verify the level of anode consumption except to weight at a very conservative density of 20 mA/m~2, which some would say closer to 8-10 mA/m~2 (to be compared with steels in concrete), with a kinetics governed by the oxygen content. The purpose is therefore to create a 1/25 scale model of a pile buried in two different types of soil (sand and bentonite) in seawater, and to follow the corrosion patterns along the pile and the need for cathodic protection current. This subject is recurrent in the consideration or not of the whole of the buried surface in order to minimize the anodic mass for a given duration. Compared to a finite element model, the objective is to make a model as realistic as possible in order to measure real correlatable quantities. The objective is to determine the current requirement at the plug depth, to ensure its protection in a buried/immersed mixed system, and to check the correct dimensioning of a cathodic protection by galvanic anodes.