<p><p>This thesis explores the possibility of alternatives to copper lining inside the water heater</p><p>tank in water heaters. The need for an alternative is based on the increasing copper prices the</p><p>recent years. The aim of this thesis is to compare three different materials, stainless steel,</p><p>copper and a nickel coated plain carbon steel. This comparison is based on a basic corrosion</p><p>test and a literature survey to render a merit value for each environment/metal interface. The</p><p>testing solution consists of 100ppm Cl</p><p>- concentration the specimens are tested in three<p>different pH levels and at three different temperatures. The specimens have their weight</p><p>measured before and after the test.</p><p>The 15μm thick nickel coating was performed by Ferroprodukter AB, composing of 9% P</p><p>and 91% Ni. The copper and stainless steel specimens are both from Thermia’s actual water</p><p>heater tank. The copper lining is made of pure copper and the stainless steel hull is made of</p><p>ferritic stainless steel.</p><p>The results from the corrosion test are measured in weight change by modulus, |Δw|/w, for</p><p>the comparison of the three materials. It was found that stainless steel was the worst</p><p>material, performing better at higher temperatures and higher pH , but overall performance is</p><p>far from copper and nickel’s corrosion properties. The nickel coating and copper specimen</p><p>showed comparable results and perform more or less equally well. Regarding identification</p><p>of corrosion mechanics, it may consist of either pitting and general corrosion damage or a</p><p>mixture of both. To avoid the fact that weight change may be both negative and positive, the</p><p>solution to this was to incorporate a merit value based on the absolute value of the weight</p><p>change, divided by the initial weight of the specimen.</p><p>In conclusion, stainless steel total weight change by modulus accumulates to 16.072g, nickel</p><p>coated specimen accumulates a weight change by modulus equal to 8.544g, important note:</p><p>two of the nickel coated specimen account for ~72.4% of the total weight change by modulus</p><p>which then accumulates to 2.36g. Copper’s total weight change by modulus was 2.937g thus</p><p>the lowest. However, disregarding from the 90캜 regime; stainless steel scores 13.496g,</p><p>copper 2.151g, and nickel 1.095g.</p></p></p>
Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:kau-3848 |
Date | January 2009 |
Creators | Wikstrand, Björn |
Publisher | Karlstad University, Division for Engineering Sciences, Physics and Mathematics |
Source Sets | DiVA Archive at Upsalla University |
Language | English |
Detected Language | English |
Type | Student thesis, text |
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