冷凝式燃气热水器中金属材料的腐蚀原因分析  

Corrosion analysis of metal materials in condensing gas water heater

作　　者：郑杰昌 钟振前 刘迎春 谢志利[1] 王慧萍[1] 李环宇 ZHENG Jie-chang;ZHONG Zhen-qian;LIU Ying-chun;XIE Zhi-li;WANG Hui-ping;LI Huan-yu(China National Institute of Standardization,Beijing 100191,China;NCS Testing Technology Co.,Ltd., Beijing 100081,China)

机构地区：[1]中国标准化研究院,北京100191 [2]钢研纳克检测技术股份有限公司,北京100081

出　　处：《冶金分析》2018年第10期34-40,共7页Metallurgical Analysis

摘　　要：某品牌家用冷凝式燃气热水器,使用期间多次出现错误报警,维修时发现冷凝水箱漏水导致主板损坏,原因是内部壳体和管路发生腐蚀。燃气热水器一旦发生腐蚀和泄漏,则存在危害人身安全的风险。因此研究其腐蚀失效过程、防止类似事件再发生意义重大。实验采用扫描电镜、能谱成分分析、金相显微镜等对某冷凝式燃气热水器的腐蚀微观形态、腐蚀产物成分和微观组织进行了分析。宏观形貌和微观分析表明,热水器在上部烟气排放口和下部进出水孔公螺纹接头两个区域发生了严重腐蚀,腐蚀位置均属于异种金属装配处,且均是电位较低的金属发生腐蚀。能谱成分分析表明,腐蚀产物中含有较高含量的硫和氧,这表明金属在含硫酸根的潮湿腐蚀性介质下发生了电偶腐蚀。金相分析表明,进出水孔公螺纹的材料组织中存在晶界析出相,降低了材料耐蚀性能,使材料发生沿晶腐蚀开裂,断裂的金属呈现掉块状剥落。因此,异种金属连接、燃气燃烧产生的硫化物以及水蒸气凝露是燃气热水器发生上述腐蚀和泄漏的主要原因。建议改进热水器组件所采用的材料,采用单一铝材制造,可以有效消除组件材料的电位差和电偶腐蚀的发生。During the use period of one brand of household condensing gas water heater,the false alarms occurred for several times.It was found in maintenance that the leakage of condensate water tank caused the damage of main board.The reason was the corrosion of internal shell and pipeline.The corrosion and leakage of gas water heater once occurred,it may cause risk to personal safety.Therefore,it was of great significance to study the corrosion and failure process,which could prevent recurrence of similar events.In experiments,the micromorphology,composition and microstructure of corrosion products of one condensing gas water heater were analyzed by scanning electron microscopy,energy spectrum composition analysis and metallographic microscopy.The macroscopic morphology and microstructure analysis showed that two areas of heater were seriously corroded,i.e.,the flue gas outlet on the top,and male connector of water inlet and outlet on the bottom.The corrosion positions were all located in assembly parts of dissimilar metals.Moreover,the corroded metals were those had lower potential.The energy spectrum composition analysis indicated that the corrosion products contained high content sulfur and oxygen,implying the bimetallic corrosion of metals in humid and corrosive medium containing sulfate.The metallographic analysis showed that the grain boundary precipitates phase existed in structure of male thread of water inlet and outlet.It decreased the corrosion resisting property of material,leading to corrosion cracking along the grain boundary.The cracked metals were peeled off in the form of small piece.Therefore,the connection of dissimilar metals,the sulfide generated in gas combustion and the condensation of water vapor were main reasons for the corrosion and leakage of gas water heater above.It was suggested to improve the materials for heater components.The fabrication using single aluminum could effectively eliminate the potential difference of material and the occurrence of bimetallic corrosion.

关 键 词：冷凝式燃气热水器 异种金属 电偶腐蚀 应力腐蚀 

分 类 号：TG141.2[一般工业技术—材料科学与工程]