亚硝酸-硝酸钠-水体系对金属材料的腐蚀行为

Corrosion behavior of nitrous acid-sodium nitrate-water system on metallic materials

建立一种亚硝酸-硝酸钠-水模拟体系,研究该体系对铝合金5A06、不锈钢0Cr18Ni9、铝锂合金1420三种金属材料的腐蚀行为,明确该体系中各因素对金属材料腐蚀行为的影响规律。设定不同的模拟体系浓度,定期对金属材料进行质量测定,并用三维视频显微镜记录其表观形貌变化。结果发现:亚硝酸-硝酸钠-水模拟体系对铝合金5A06、铝锂合金1420具有明显的腐蚀性;金属在该模拟体系作用下质量持续下降,但在一段时间后不再变化,金属表面出现腐蚀性坑洞与腐蚀斑迹;该模拟体系对不锈钢0Cr18Ni9几乎没有腐蚀;硝酸钠-水溶液会使铝合金5A06、铝锂合金1420材料表面形成氧化膜而增加其质量,一段时间后质量不再增加,说明硝酸钠对这两种金属只有氧化作用而无剥蚀行为,因而亚硝酸-硝酸钠-水模拟体系可近似等同于亚硝酸-水腐蚀体系;在亚硝酸浓度较低的情况下(≤0.167 mol/L),铝合金5A06和铝锂合金1420在亚硝酸-硝酸钠-水模拟体系中符合近似线性的腐蚀加速规律。

The nitrous acid-sodium nitrate-water system was established to investigate corrosion behavior of the system on three metal materials: aluminum alloy 5 A06,stainless steel 0 Cr18 Ni9 and aluminum-lithium alloy 1420, and to determine the influence rule of corrosion behavior of each factor in the system on metal materials. The different simulation system concentrations were set, and mass determination was conducted regularly for metal materials. Besides, the apparent morphology changes of metal materials were recorded with 3 D video microscope. The results showed the nitrous acid-sodium nitrate-water simulation system was obviously corrosive to aluminum alloy 5 A06 and aluminum-lithium alloy 1420. The metal mass continued to decrease under the action of the simulation system,but no longer changed after a period of time. Besides, corrosive holes and corrosion stains on the metal surface appeared. The simulation system almost had no corrosion to stainless steel 0 Cr18 Ni9. Further research found that sodium nitrate-water solution could make aluminum alloy 5 A06 and aluminum-lithium alloy 1420 form an oxide film on the surface of materials to increase its mass. After a period of time, the mass no longer increased, indicating that sodium nitrate only oxidizes the two metals and has no corrosive behavior. Therefore, the nitrous acid-sodium nitrate-water simulation system can be approximately equivalent to the nitrous acid-water corrosion system. In the case of low nitrite concentration(≤0.167 mol/L), the aluminum alloy 5 A06 and the aluminum-lithium alloy 1420 accords with an approximately linear corrosion acceleration law.