ABSTRACT

For most projects, cathodic protection (CP) design can be performed using CP standards or existing data from literature and field feed-back. It was not the case for the particular environment of the YAMAL gas carrier terminal project, planned in Sabetta (Siberia - Federation of Russia). This particular area is located between the Kara sea and a river mouth in Yamal peninsula (Artic region). It involves very different conditions in terms of salinity, temperature, liquid/ice phases, all depending on icing/deicing seasons and on the water depth. These very specific conditions can hardly be simulated at laboratory scale and required a specific corrosion and CP study with measurements on site. The global aim of this quantitative study was to collect field data to help at defining an adapted corrosion protection system for carbon steel immerged structure (e. g. berths), and to forecast the related corrosion risks. Regarding the extreme conditions of the site, the main challenge was to design adapted arrays containing corrosion and CP sensors (to be deployed on site), to get representative quantitative data. All systems have been qualified at laboratory scale before use on field site. The deployment was successful and allowed getting actual polarization curves, and local initial corrosion data. In parallel, the stability of zinc galvanic anodes has been evaluated in this resistive environment. For both corrosion and CP data, different results have been highlighted for surface and bottom waters, and for ice & liquid phases. Modelling can now be used to assess the efficiency and select the CP system (i. e. galvanic anode or impressed current).

INTRODUCTION

Total is partner of the Yamal LNG project and has been involved in the cathodic protection design of the berths. Given the harsh local conditions, the possibility to protect the berths by galvanic anodes was considered as the preferred solution. Nonetheless the water is brackish water, and as such it can impact significantly the design with galvanic anodes. It was thus considered as mandatory to obtain accurate current densities requirement to achieve an efficient cathodic protection.

The particular environment of Yamal terminal located in Sabetta (Yamal Peninsula - Federation of Russia) involves indeed different conditions (salinity, temperature, liquid/ice phases) depending on icing/deicing seasons and on the water depth (e. g. ice on surface along the first meters during cold season and liquid phase above the water floor, and different salinity from surface water to deeper water, especially during summer season). These very specific conditions required a specific corrosion study with measurements on site, aiming at characterizing the corrosivity and the cathodic protection (CP) requirements of immersed carbon steel used for structures in the gas carrier terminal (berths and/or steel sheet piles).

This content is only available via PDF.
You can access this article if you purchase or spend a download.