CoatingsPro Magazine

NOV 2018

CoatingsPro offers an in-depth look at coatings based on case studies, successful business operation, new products, industry news, and the safe and profitable use of coatings and equipment.

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Page 43 of 76

COATINGSPRO NOVEMBER 2018 43 Science Behind It High-Temperature Coating Technology By Alexander Prince, Vice President of Belzona New York, LLC T he costs of corrosion can be colossal, especially where safety critical equipment is concerned. W hen looking at the expenses associated with corrosion, particularly in the power industry, direct and hidden costs should be considered. e former includes equipment and part replacement whereas the latter accounts for downtime, delays, litigation, and other unplanned overheads. Corrosion occurs when three elements are present in an environment. ose are a cathode (a negatively charged conductor), anode (a positively charged conductor), and electrolyte (a liquid that conducts electricity). And other factors, including oxygen, temperature, and water, can increase corrosion. In a deaerator tank system, those three play a part. Corrosion Persists Process vessels in t he power industr y common ly e x per i- ence high-temperat ure ser v ice. Ma ny insta nces a re in f u l l immersion, but t he ha rsher env ironments a re found in vessels t hat a re consta nt ly in f lu x. For e x a mple, deaera- tor ta n k s feat ure a water storage a rea t hat is consta nt ly f i l l ing up a nd empt y ing , whic h mea ns t hey have va r y ing water levels. A deaerator tank takes oxygen out of a system. In the case of Tower Maintenance Corp.'s work at the Westchester Department of Public Works and Transportation, it was for power. Deaerator tanks remove the air oxygen out of the system so that other areas, including pipelines, are protected. e tank is a sacriĆ’cial piece of the system, but it also needs to be protected from pitting. T he area w ith the most cause for corrosion on a deaer- ator tank is what is commonly know n as the water line. T his area is the band of surface on the tank that covers the lowest level to the highest level where the liquid is in constant f lu x. T his is the area on all vessels/tanks that features the worst corrosion, and it is always the first area in jeopardy of failing. T his is for the same reason that you don't want air in your heating system in your house: If you have air in your hot water system, cold spots w ill occur. Similarly, on a deaerator tank, the area where there are spots of ox ygen and constant cycle of condensing and dr y ing, corrosion persists. A reas of full submersion, on the other hand, are less in danger. Service Vessel Protection ere are several key reasons why unprotected steel on these vessels fails amid this high-temperature service. ese include: y Fluctuating water lines. The changing water line promotes surface corrosion, which will lead to deep pitting. If maintenance is avoided, this will lead to metal loss that could compromise the useful life of the tank. y T he tank is a lways in ser v ice. A sset ow ners don't rea lize how impor tant a deaerator tank is unti l it goes of f line because it puts stress on other par ts of the system or ma kes it impossible to meet the demands. T his means that the tanks are in constant ser v ice and, therefore, constant ly being ex posed to those cor ro - sion-inhibiting factors. ese reasons make a proper barrier or coating on the water line, an area that experiences the most attack from corrosion, a crucial component in extending the life cycle of the steel surface. Put It to the Test! T here are many key benefits to asset ow ners to use high-temperature coatings, including simplif y ing maintenance procedures, reducing the need for annual maintenance, cutting dow ntime, and improving safety by reducing hot work. T his ty pe of technolog y has the ability to resist corrosion and chemicals while operating under immersed conditions. T he most recent developments in epox y coating technolog y offer notable protection in the harshest environments. T he most effective coatings offer complete compatibility w ith epox y fillers and rheolog y character- istics that allow for material f low-out for more control when brush applied, resulting in more uniform film thick- ness. Additionally, the latest generation of epox y includes special plasticizers to allow for expansion and contraction. Without this, coatings tend to crack, and the delamination process begins. T he big challenge is to find the right balance of these desirable characteristics that must also include high cross linking for temperature protection and chemical resistance. W hen a coating is engineered, all of this and more must be taken into consideration before they can truly become best in class. CP

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