IMPROVEMENT OF CORROSION RESISTANCE OF SHEET PILING IN SEAWATER

摘要

Development of structural steels with improved corrosion resistance is gaining significance for use in offshore structures. Corrosion of structural steel depends not only on various influencing factors such as location of seaport or seawater corrosivity zone the steel is exposed in, but also on the chemical composition of the steel itself. Against this background the influence of alloying additions of copper, chromium and nickel, which are known to be able to mitigate corrosion by seawater, was investigated aiming at an economic alloy modification of structural steels used for manufacture of sheet piling. Laboratory corrosion tests were conducted with the rotating cage test setup. As a reference the corrosion performance of standard structural steel grades in the strength range of 275 MPa to 500 MPa was determined. The influence of alloying additions of copper, chromium and nickel was investigated in further tests using industrially manufactured sheet piling including a steel manufactured in accordance with ASTM A 690. From the investigated alloy variants, the steels alloyed with about 0.3 % copper were found particularly suitable for reduction of general corrosion in seawater by up to 36 %. In order to ensure the workability of copper alloyed components, usually an adequate amount of Ni is added. However, the corrosion test results, e.g. for the copperickel alloyed steel ASTM A 690 showed that such a measure is not recommended if improved corrosion resistance in seawater is envisaged.