RIASSUNTO
ABSTRACT
Two types of corrosion cause the majority of problems in offshore or seawater applications; aqueous corrosion and microbiologically influenced corrosion (MIC). Aqueous corrosion results from the alkalinity of the seawater itself where MIC degradation stems from microorganisms in the seawater that cause corrosion and stress cracking in materials. Rotational lining solutions can apply a thick, fully bonded, vacuum resistant, monolithic liner of high-density polyethylene (HDPE) to the inner diameter of piping systems, and has proven to provide long-term corrosion protection to aqueous corrosion in saltwater applications. To combat MIC, a novel combination of antimicrobial powder and high-density polyethylene powder was applied through rotational lining. Experiments were conducted to evaluate the biological and mechanical performance of material coatings. Results from microbiological testing showed that coatings enhanced with the material resisted and deactivated over 99% of bacteria while results from mechanical testing indicated that the additive has no significant impact on the corrosion or abrasion resistance of the HDPE lining or on the adhesion of the lining to the substrate. These results are significant because the additive material eliminates the primary source of MIC while maintaining the mechanical and thermal properties of the existing HDPE coating system. This technology provides transformative change in treatment and prevention methods for offshore and seawater applications.
INTRODUCTION
Microbiologically influenced corrosion (MIC) is responsible for over 40% of equipment failures in oil and gas production, processing, and transport equipment. Additionally, MIC significantly impacts water distribution systems, shipping and additional industries that rely on non-metallic and metallic materials. In this type of corrosion, microorganisms cause corrosion and stress cracking in both metallic and nonmetallic materials by forming colonies and eating away at the material surface. MIC has been well documented in substrates exposed to a variety of aqueous environments including seawater, freshwater, soils, and fuels [1-3]. The majority of MIC is caused by sulfate-reducing bacteria (SRB) [46]. These bacteria can also combine with other bacteria and form a more complex biofilm [7]. Biofilm- metal interactions at the molecular level have yet to be completely understood. The growth of biofilms and subsequent MIC damage also increase skin friction drag of ship hulls [4, 8] and feeds the attachment of sessile marine invertebrates [4, 9], which directly, negatively impacts the ships' fluid drag resistance performance and increases energy requirements. The cost of corrosion in the US rose to over $1 trillion in 2013 making corrosion one of the largest single expenses in the US economy [10]. MIC and related activities contribute to almost 25% of the total US annual cost of corrosion [4, 11-12]. When this degradation is combined with aqueous corrosion from the marine environment, it is apparent that any significant advancement in MIC mitigation would prove invaluable to asset protection programs in seawater applications.