SAFETY

There is a special safety concern when using zirconium. Reactive metals like zirconium can develop pyrophoric films. Normally zirconium corrodes uniformly and all the zirconium is converted to zirconium oxide. If corrosion rates are low, <5 mpy, there is time to react all the zirconium uniformly. For very high corrosion rates, >200 mpy, the reaction rate is so high that all zirconium is also reacted. At certain conditions, it is possible that the corrosion rate will attack grain boundaries and continue attacking the boundaries, trapping small pieces of Zr grains in the oxide and not completing the oxidation. Under these conditions, the oxide film may be pyrophoric. To passify the zirconium, the trapped zirconium pieces need to be completely oxidized before opening the equipment to air. This is achieved by passing hot air or steam through the equipment to make sure all the zirconium in the oxide film is reacted before opening to air. At 250¡C, air must flow for 20 minutes or steam for 30 minutes; at lower temperatures, several days of treatment are required.

SUMMARY / CORROSION LAB SERVICES AND OTHER WAH CHANG RESOURCES

As demonstrated above, zirconium can be the best alternative for material selection in chloride salt solutions, including seawater systems. Longer equipment life, reduced maintenance downtime, and higher purity product streams are all possible with the proper application of zirconium, making it the most cost-effective option when compared with other alloys. Although zirconium has proven its outstanding corrosion resistance performance in a wide variety of chloride salt solutions and seawater applications, the best way to determine zirconiumÕs suitability for a particular environment is to perform a corrosion test. Zirconium corrosion test kits are available from Wah Chang for use in on-line process equipment. These tests can show how zirconium will hold up under actual process conditions. Wah Chang also has a fully capable corrosion laboratory for complete testing and detailed analysis for specific chloride salt solutions or seawater applications. For further information or any questions regarding the use of zirconium in chloride salt solutions or seawater applications, please contact the Technical Services Division at Wah Chang, phone 541-917-6777 fax 541-967-6987.

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