文章信息/Info

Title:

In�睸itu Monitoring the Pitting Corrosion Process of GW93 Mg Alloy and Related Pitting Corrosion Mechanism

文章編號(hào):

1674-3962(2020)02-0085-07

作者:

宋影偉; 樊志民; 董凱輝; 單大勇; 韓恩厚

（中國(guó)科學(xué)院金屬研究所 核用材料與安全評(píng)價(jià)重點(diǎn)實(shí)驗(yàn)室，遼寧 沈陽(yáng) 110016）

Author(s):

SONG Yingwei;  FAN Zhimin;  DONG Kaihui;  SHAN Dayong;  HAN En�睭ou

(Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China)

關(guān)鍵詞:

鎂合金; 點(diǎn)蝕; 第二相; 掃描振動(dòng)電極; 原位監(jiān)測(cè)

Keywords:

Mg alloy;  pitting corrosion;  second phase;  scanning vibrating electrode technique;  in�瞫itu monitoring

分類號(hào):

TG174

DOI:

10.7502/j.issn.1674-3962.201908038

文獻(xiàn)標(biāo)志碼:

A

摘要:

鎂合金作為最輕的金屬結(jié)構(gòu)材料有很多優(yōu)異性能，但鎂自身化學(xué)性質(zhì)活潑，耐蝕性差，尤其易發(fā)生點(diǎn)蝕，破壞性和隱患性非常大。若想降低點(diǎn)蝕對(duì)鎂合金部件安全服役性能的影響，就需要對(duì)鎂合金點(diǎn)蝕機(jī)制有清楚的認(rèn)識(shí)。然而，適用于其他金屬材料的經(jīng)典的點(diǎn)蝕機(jī)制是以形成氧濃差電池為基礎(chǔ)，陰極發(fā)生的是氧還原反應(yīng)，而鎂合金陰極發(fā)生的是析氫反應(yīng)，因此鎂合金的點(diǎn)蝕形成過(guò)程尚需深入研究。采用掃描振動(dòng)電極技術(shù)(SVET)原位監(jiān)測(cè)了鑄態(tài)GW93鎂合金在3.5% NaCl（質(zhì)量分?jǐn)?shù)）溶液中的點(diǎn)蝕過(guò)程，采用SEM觀察了腐蝕過(guò)程鎂合金微觀形貌變化，采用電流-時(shí)間曲線對(duì)比了陰陽(yáng)極電位對(duì)點(diǎn)蝕發(fā)展的影響。研究結(jié)果表明，點(diǎn)蝕坑外是微陰極，發(fā)生析氫反應(yīng)，點(diǎn)蝕坑內(nèi)是微陽(yáng)極，發(fā)生鎂的溶解反應(yīng)，隨著時(shí)間增加，點(diǎn)蝕發(fā)展過(guò)程是動(dòng)態(tài)變化的。鎂合金中第二相所導(dǎo)致的微電偶腐蝕加速效應(yīng)及氯離子在腐蝕坑內(nèi)的聚集，兩者的協(xié)同作用驅(qū)動(dòng)了點(diǎn)蝕不斷向基體內(nèi)部生長(zhǎng)。

Abstract:

Mg alloys, as the lightest structural metallic materials, have many excellent properties. However, the chemical activity of Mg is high, resulting in poor corrosion resistance. Especially, Mg alloys are susceptible to pitting corrosion with great destructiveness and hidden danger. To decline the negative effect of pitting corrosion on the safe service of Mg alloy parts, it is necessary to clarify the pitting corrosion mechanism of Mg alloys. The classical pitting corrosion mechanism of other metals is based on the formation of oxygen concentration cell, whereas cathodic hydrogen evolution reaction occurs on Mg alloys. Thus, the pitting corrosion process of Mg alloys needs to be investigated in detail. In this paper the pitting corrosion process of GW93 cast Mg alloy is monitored in-situ using SVET (scanning vibrating electrode technique) in 3.5% NaCl solution; the corrosion morphologies are observed using SEM (scanning electron microscopy); and the effect of cathodic and anodic potentials on the pitting corrosion process is compared using electrochemical measurements. The results indicate that the microcathodes locate in the outside of corrosion pits and hydrogen evolution reaction occurs there, while the microanodes locate in the interior of corrosion pits and Mg dissolution reaction occurs. The pitting corrosion process dynamically changes with increasing corrosion time. The synergistic effect of the microgalvanic acceleration resulted from second phases and enrichment of chloride ions in corrosion pits is the driving force for the propagation of corrosion pits towards the interior of Mg substrate.