(1.浙江大學(xué) 化學(xué)系， 杭州 310027;
2.中國(guó)科學(xué)院 金屬研究所 金屬腐蝕與防護(hù)國(guó)家重點(diǎn)實(shí)驗(yàn)室，
沈陽(yáng) 110015)
摘 要: LC4鋁合金在2.0%NaCl溶液中發(fā)生局部腐蝕的過(guò)程中，電位噪聲的譜功率密度(SPD)曲線具有相同的特征，即在極低頻下為白噪聲，隨著頻率的升高逐漸轉(zhuǎn)化為1/fa噪聲，相應(yīng)于一個(gè)噪聲信號(hào)波，有一個(gè)腐蝕孔出現(xiàn)。在孔蝕誘導(dǎo)期，白噪聲水平升高，截止頻率增大， SPD曲線的傾斜段直線斜率小于-25dBv/Hz，且趨于增大。孔蝕發(fā)生后， 上述3個(gè)參量則各自朝著上述方向的逆方向變化。實(shí)驗(yàn)發(fā)現(xiàn)，孔蝕參數(shù)SE和SG可以正確的表征孔蝕的發(fā)生、發(fā)展及材料的均勻腐蝕。阻抗測(cè)量結(jié)果表明：孔電阻在剛開(kāi)始浸泡時(shí)較大，隨后減少漸趨于平穩(wěn)，最后孔電阻又升高。這是因?yàn)殡S著浸泡時(shí)間的增加，孔面積漸漸增大，浸泡65000min時(shí)，孔電阻有所上升，可能是由于母孔內(nèi)子孔的形成所致。 產(chǎn)物電阻逐漸穩(wěn)定上升，表明腐蝕產(chǎn)物逐漸增多。
關(guān)鍵字: LC4鋁合金；孔蝕；電化學(xué)噪聲；電化學(xué)阻抗譜；等效電路
during pitting corrosion of LC4 aluminum
alloy in 2.0% NaCl solution
ZHANG Jian-qing1, 2，WANG Jian-ming1, CAO Chu-nan1, 2
（1. Department of Chemistry，Zhejiang University，
Hangzhou 310027，China;
2. State Key Laboratory for Corrosion and Protection, Institute of
Metal Research, Chinese Academy of Sciences, Shenyang 110015, China）
Abstract:The features of electrochemical noise (EN) of super-strength LC4 aluminum alloy in 2.0%NaCl solution during pitting corrosion were investigated. The results show that all the ENs observed are low frequency noises and the white noise(Pw) which is independent of frequency in the super low frequency domain and changes to the 1/fa noise with the increasing of frequency. Each pit on the surface of corroding electrode corresponds to sudden jump of electrode potential in time domain. During induced duration of pitting corrosion ，the level of white noise and the value of cut-off frequency (fc) increase with the increase of immersion time，while the absolute value of slope of SPD curve's linear part decreases. On the other hand，the above three parameters change in the opposite direction after a pot or a series pits are formed. Based on the EIS displays of LC4 aluminum alloy at various immersion time，one kinds of equivalent were proposed as their physical models. The relation between impedance characteristics and structure and properties of oxide film were discussed.
Key words: LC4 aluminum alloy; pitting corrosion; electro chemical noise; electrochemical impedance spectroscopy; equivalent circuit
