The Effects of Chlorine on Boiler Corrosion

The amount of corrosion of six metal samples was measured by a change in weight over time. The simulated flue gas stream consisted of 0.2% SO2,14% C02 / and 4% O2, with the HC1 percentage varied from 0.2% to 0.0% and the balance of gas being N2. A Lindbergh Three Temperature Tube Furnace was used to house the metal samples at 100°C, 200°C, and 600°C while being subjected to the simulated flue gas stream. The six metal samples were chosen on the frequency of industrial use. Two carbon steels, C1018 and C1010, contain no chromium and were chosen because of their popularity in older coal combustor systems. The other four samples, F l l , F22, Alloy 800, and 310 SS, are chromium containing metals that were chosen to indicate corrosion inhibitory effects. These four chromium containing samples are commonly used for replacement parts in areas that are prone to high corrosion effects. Weight loss due to corrosion shows a direct relationship to the concentration of HC1 in the flue gas stream for the F l l , F22, and C1018 samples. The greatest amount of weight loss was seen in the 0.2% HC1 and the least for the three samples when there was no HC1 in the flue gas stream. The C1010 sample had the greatest amount of weight loss under the 0.01% HC1 concentration, slightly less for the 0.2% HC1, and finally a weight gain for the 0.0% HC1 run. At no concentration did samples Alloy 800 and 310 SS exhibit any weight change. As for temperature considerations, the greatest amount of change in the samples was seen for the 600°C runs. The 200°C run produced no change in weight for any of the samples, due to the lack of condensation that would facilitate corrosion at low temperatures. For the 100°C runs, the flue gas containing 0.2% HC1, 0.2% S02,14% SO2,4% O2, and the balance N2, caused a change in weight for F l l , F22, C1010, and C1018. This change was not as great as that for the 600°C run. The other two 100°C runs produced no change in weight. Chromium content of the metals can also be related to the amount of corrosion. The high percentage chromium metals, Alloy 800 and 310 SS, showed no weight change in any of the runs. Low chromium containing samples, Fll and F22, showed a loss of weight at all 600°C runs and also for the 100°C subjected to the 0.2% HC1 flue gas stream. The C1010 and C1018 samples contain no chromium and have the most erratic results. These samples gained in weight for the 600°C run for the 0.0% HC1 gas and lost weight for the two other 600°C runs. Also, weight loss for these samples was observed for the 100°C run under 0.2% HC1. Corrosion of the samples begins and proceeds rather quickly until an oxide layer is formed. Once the oxide layer has formed, the amount of corrosion is dependent on the stability of that layer and the diffusion rate of the gases