Harsh environmental conditions prevail in most petroleum pipelines as well as downhole tubulars. Under these conditions, corrosion can have adevastating effect on both petroleum production and transportation. The petroleum industry has been using inorganic zinc coating as a primer coating that can withstand prolonged services. It is well known that zinc reacts with steel to form a very strong bond that is not easily broken when subjected to HARSH CONDITIONS. However, several areas of weakness persist. There is no existing method to select the most effective primer among many that are available commercially. The current methods do not optimize the thickness of the primer and the mechanisms of corrosion prevention in the presence of abrasive materials are not well understood. This paper addresses these shortcomings of the past and proposes a comprehensive technique for corrosion prevention in harsh environmental conditions.
In a series of experiments, corrosion (both onset and growth) is observed in various pH conditions using various thicknesses of zinc primers. In order to simulate solid/solid interaction (e.g. pipeline in an environment where sands and dusts prevail), sand blasting is performed for a predetermined period. In this, the time of sand blasting was considered to be crucial since the time in the laboratory must be scaled down to model field conditions. For different cases, the nature of corrosion and the extent of growth were observed both in the presence and absence of top coatings. The extent of corrosion under sand abrasion was also observed. A procedure is recommended for determining optimum thickness of zinc primers under various environmental conditions (e.g. pH, sand erosion). Top coatings were found to be necessary for several of the conditions. Fundamental chemistry as well as fractal modeling is used to define the kinetics of corrosion growth. The role of zinc primer in developing a barrier is incorporated. The study results compare favorably with the experimental results