文章信息/Info

Title:

TEM study on the pitting initiation

作者:

張波; 馬秀良

中國科學院金屬研究所，遼寧 沈陽 10016

Author(s):

ZHANG Bo;  MA Xiuliang

Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China

關鍵詞:

點蝕; 結構缺陷; 鈍化膜; 透射電子顯微學; 原子尺度

Keywords:

pitting;  structural defects;  passive film;  TEM;  atomic-scale

DOI:

10.7502/j.issn.1674-3962.2018.11.04

文獻標志碼:

A

摘要:

鈍性金屬材料的點蝕是腐蝕領域中的經典問題。受研究手段空間分辨率的限制，點蝕形核階段的機制有待進一步闡明。本文以透射電子顯微技術為主要研究手段，圍繞與點蝕形核密切相關的材料基體結構特征及鈍化膜性質兩方面展開，闡明了點蝕形核的基體結構相關性以及鈍化膜結構及與Cl-的交互作用兩大基本科學問題。在原子尺度下建立了材料基體結構特征與腐蝕溶解活性之間的關聯，揭示了鈍化膜的結構特征與Cl離子與之交互作用之間的內在規律，豐富、完善甚至修正了材料點蝕形核機制方面的經典認識。研究發現，在點蝕形核初期，無論是基體中夾雜或第二相的腐蝕溶解活性，還是表面鈍化膜本身的擊破，其起源都可以追溯到原子尺度的結構缺陷。

Abstract:

Pitting corrosion of passive metals is a classic issue in corrosion field. Over the past decades, the mechanism of pitting corrosion has attracted corrosion community striving to study. However, the mechanism at the pitting initiation stage is still controversy, due to the difficulty encountered in obtaining precise experimental information with enough spatial resolution. Using transmission electron microscopy, we focus on the structure of matrix and the nature of passive film, which are closely related to pitting initiation. This work clarifies the structural origins of the pitting initiation and unmasks the mechanism of chloride-induced passivity breakdown. At the pitting initiation stage, the heterogeneous corrosion activity of inclusions/second phase in matrix, and the preferential attack of the passive film are originated from the atomic-scale structural defects. This work enriches, improves and even modifies the classical understanding on the pitting initiation mechanism.