臺北自來水事業處陽明轄區自來水管腐蝕型態分析

Analysis of Corrosion Types for Water Pipe in Taipei Water Department Yangming Branch Served Area

孫文益(Wen-Yih Sun)

指導教授 ： 張永鵬

中原大學/工學院/機械工程研究所/碩士(2005年)

https://doi.org/10.6840/cycu200500018

摘要

國內自來水事業單位對於埋設於地下，直接與土壤及水等腐蝕介質接觸的金屬管線，長期以來欠缺有系統的針對腐蝕原因進行調查及整理，面對未來水資源的可能匱乏、供水系統壓力昇高的需要、自來水生飲計劃的推動及民眾對飲水品質的重視等議題，必須對自來水管腐蝕型態加以了解，以採取適當的防蝕方法，來確保自來水的品質及降低漏水的發生。
本研究針對臺北自來水事業處陽明分處供水轄區所作之土壤腐蝕性調查，得致市場及硫磺區一帶土壤腐蝕性達嚴重程度，是腐蝕行為最易進行之處，針對這些地區必須加強管線外部防蝕措施。而從拆回破損管材以掃描式電子顯微鏡(SEM)及能量分散式光譜儀(EDS)進行之腐蝕原因分析結果，鑄鐵管內部腐蝕明顯比外部腐蝕嚴重，這種情形在管件更為明顯，原因是管件內襯塗裝不良所致，而鑄鐵管主要的腐蝕型態是石墨化，並可由放大石墨化層的形狀來判斷是灰口鑄鐵還是延性鑄鐵材質；從取樣之不銹鋼管外部破損情形，研判為間隙腐蝕，這類型腐蝕大都發生於管身外部局部的不良包覆，在包覆處產生間隙而誘發，實際上，不銹鋼管在氯含量高的土壤中可能發生孔蝕、雜散電流密度高的區域也可能誘發電蝕現象，只是未加注意，目前臺北自來水事業處五個轄區，不銹鋼管埋設長度合計僅佔所有給水管線長度之13%，應儘早蒐集相關腐蝕樣本，建立分析資料，以利採取防蝕對策。

關鍵字

自來水管 ； 腐蝕 ； 腐蝕型態 ； 土壤腐蝕性

並列摘要

Water mains of metal pipelines are normally used to transport tap water. However, quite few surveys and inspection in corrosion were studied for water mains in Taiwan. Facing on the shortage of water resource and achievement of safe drinking program, it is necessary to understand the corrosion types of metal pipelines and have a systematical survey to prevent leakage. Since corrosion of metal pipelines are dominant factors to cause water pipeline leakage, corrosion prevention and materials selection for metal pipelines become important.

In the present study, specific attention has been focused upon corrosivity of the soil in Taipei Water Department Yangming Branch served area. In addition, corrosion types of metal pipelines was investigated. It is found that the soil in the Yangming Branch area is very corrosive at traditional market and hot spring areas, where corrosion of metal pipelines is severe. Consequently, it should pay more attention to have corrosion protection. For corrosion type analysis, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were applied. It indicates that corrosion of cast iron pipe is serious in interior side of pipeline compared to exterior side. Especially for fittings, bad coating on interior surface is the reason to cause corrosion. For cast iron pipeline, the corrosion type is graphitization. By magnification of graphitization layer, either gray cast iron or ductile cast iron can be identified. For stainless steel pipeline, the corrosion type is crevice corrosion that occurs when coating or wrapping of pipeline is defective.

Recently, stainless steel pipeline has been widely used in water utility in Taipei City. According to statistic data from Taipei Water Department, 13% of service pipelines in Taipei are stainless steel. To prevent water leakage from stainless steel pipelines, except crevice corrosion, pitting corrosion and stray current corrosion should be noticed. Therefore, establishment of corrosion database followed by selection of corrosion control methods for water utility is important.

並列關鍵字

corrosion ； water pipe ； corrosivity of the soil ； corrosion types

參考文獻

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