Materials Performance

MAR 2017

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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52 MARCH 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 3 MATERIALS SELECTION & DESIGN T A corrosion analysis of a newly in- stalled domestic (residential) heating system was carried out after it suf- fered corrosion attack in less than three months of operation. The make- up water had a high salt concentra- tion and a low pH value. In addition, the make-up water had high oxygen concentration and hardness. A pro- tective rust layer in the inner pipe sur- face was not formed during a short operation period. Replacing the high- salt water with low-salt water as the make-up water, ensuring that the de- livery pipe is full of water, evacuating any air in the pipe, and introducing additional corrosion inhibitor to the delivery water should be considered. To e n su re t h e st a b i li ty of a f a m i ly heating system, it is important to deter- mine and discuss any corrosion causes and then provide suitable recommendations. There are numerous small-scale heating systems in which proper water condition- i n g (d e oxyge n a t i o n a n d s of t e n i n g ) i s completely absent. According to available data, for example, more than 1,000 such systems operate in the Kuzbass industrial region (Siberia, Russian Federation), 1 and n eith er dea eration nor soft ening have been employed to the hot water supply sy st ems linked w ith such h eat supply systems. 2 A newly installed rural domestic heat- ing system was suffering from corrosion attack after less than three months of oper- ation. This severely affected the safe opera- tion of the heat supply system. A corrosion investigation and analysis were carried out, with visual obser vations including p h o t o g r a p h s . P r o p e r r e m e d i e s w e r e recommended. Visual Observations/ Experiments Visual Observations and Water Quality Analysis The make-up water for this heating sys- tem is taken from an underground supply (i.e., groundwater). The owner states that the water tastes salty ; and after boiling, scale deposits coat the vessel. It was con- cluded that the subject groundwater con- tains significant amounts of dissolved sol- ids. Additionally, the owner states that the underground water from his neighbor's property contains a lesser amount of dis- solved salts. Analysis indicates that the high-salt water contains 200 mg/L of sul- fate ions (SO 4 2– ), 142 mg/L of chloride ions (Cl – ), 56 m g/L of calcium ions (Ca 2+ ), 22.8 mg/L of magnesium ions (Mg 2+ ), and 11 mg/L of dissolved oxygen (DO); has a hardness of 850; and has a pH of 6.3 to 7.0. 3 The low-salt water contains 157 mg/L of SO 4 2– , 106 mg/L of Cl – , 40 mg/L of Ca 2+ , 15.2 mg/L of Mg 2+ , and 10 mg/L of DO; has a hardness of 600; and has a pH of 7.0 to 8.5. Clearly, the high-salt make-up water con- tains a larger amount of SO 4 2– and Cl – , and has higher hardness value and lower pH value than the low-salt water. Corrosion Analysis of a Newly Installed Family Heating System Z H anjun g uo, Institute of Environmental & Municipal Engineering, North China University of Water Resources and Electric Power, Zhengzhou, China Z H iliang C H en, Yangzhou Research Academy of Energy and Material, Chinese Academy of Sciences, Yangzhou, China † Trade name.

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