Materials Performance Supplements


Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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Traditional water treatment methods pose several challenges to large- vessel preservation. The economics of continuous dosing and environ- mental restrictions concerning the disposal of treated water need to be considered. One solution to these challenges involves the application of an immiscible corrosion inhibiting oil partition on the water surface (hence- forth referred to as a "float coat"). This article highlights the challenges of traditional preservation methods and examines the efficacy of one commercial float coat. Large vessel preservation is typically accom- plished through one of two methods: chemical treatment of water during hydrotesting or heavy-duty epoxy coating systems. These treatment systems have proven to be effective. However, novel approaches to large vessel preservation provide an op- portunity to overcome challenges in- volved with more traditional preser- vation methods. Th ere a re va ri o u s wat er tre atm ent methods available to protect large storage vessels from corrosion , including those used in the petroleum industry. This article describes common methods and presents testing information and conclusions about a coating technology that is cost-effective, environmentally friendly, and suitable for large vessel protection. Preservation Methods Chemical Treatment Aboveground storage tanks (ASTs) in the petroleum industr y come in a wide variety of sizes, ranging from modest sizes of 200 m 3 up to storage volumes in excess of 100,000 m 3 . 1 For even the most modest dos- age rates of chemical treatment at 500 ppm, costs can exceed $2.5 million USD for more than 115 m 3 of chemical treatment. Coatings Coatings can be separated into remov- able, or "temporary" coatings, and perma- nent coatings. After the application of either type of coating, the proper amount of cure time must be allowed for the coating to achieve peak performance. Typical recom- mendations call for one week of cure time. During this time, no maintenance or testing can be performed on coated areas, resulting in lost time and productivity. For tanks with a 91.4-m diameter and 18.3-m wall height, 1 the total wall surface area is approximately 5,300 m 2 . Given a spread rate of 3.7 m 2 per liter, over 1,500 L of the coating are required, costing upwards of $40,000. While removable or temporary coatings typically cost less than permanent coatings, the reapplication of any coating for long-term preservation would require significant labor cost for surface prepara- tion and application. Finally, lost time ( for product application and cure time) is also a considerable factor, resulting in lost profits. Waste Disposal Wa st e di sp o sal and env ironm ent al concerns can be very large factors in deter- mining the efficacy of any procedure whose processes produce any amount of poten- tially hazardous chemical waste. The cost to properly dispose of "dirty water waste" ranges from $0.04 to $0.24 per cubic m 3 . 2 Given a tank size of 100,000 m 3 , waste dis- posal can add up to $24,000 onto existing project costs. Though more modest-sized containers would significantly reduce the cost for waste disposal, this expense still remains a major consideration in the effi- cacy of any given treatment. Application of a Float Coat A f loat coat is a corrosion-inhibiting oil that is applied to a large-volume sys- tem during a typical hydrotesting process. The float coat, being a hydrocarbon-based product, floats on the surface of the water, allowing for a unique application using a much smaller volume of product than typi- cal chemical additives. The vessel f loor and initial meter of wall height is sprayed with a layer of the float coat before any water is added to the system. Water is slowly added, until a point just below the initial spray treatment, so to avoid disturbing the applied float coat pro- tective coating. The remainder of the float coat is applied to the top of the water layer. Hydrotesting is then carried out as nor- mal with care to fill the system at such a rate that the float coat layer on the water's surface is not disturbed. As the hydrotest proceeds, the walls of the vessel are coated with the float coat and further recoated as the vessel is drained. Experimental Procedures Using a f loat coat has proven to be a viable preservation technique for ASTs and other large vessels during hydrotesting via Using a Float Coat for Preservation of Large-Volume Storage Systems John Wulterkens and Casey h eurung, Cortec Corp., St. Paul, Minnesota, USA h oussam s abry, ADGAS, Abu Dhabi, United Arab Emirates PROTECTIVE COATINGS 10 JUNE 2017 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP CORTEC SUPPLEMENT TO MP

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