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低合金钢在3.5％NaCl中恒电位阳极极化能模拟在海水中腐蚀时各微区部位的电化学过程。用这种加速方法可以增加发生在各微区上的中间产物的相对含量。作者应用穆斯堡尔效应探测到这些微量中间产物,从而掌握目前还不能直接测定的,在海水中试样上阻挡层铁锈的相组成。研究结果表明,不同低合金钢具有不同的阻挡层铁锈相组成,它们除了都具有海水腐蚀后试样所持有的β-,γ-FeOOH终态相外,还分别具有不同组份的,呈微晶或无定形的一类似于绿锈Ⅰ,Fe_2(OH)_3Cl等的中间态铁锈。这些中间态铁锈在空气中极易氧化、脱水、时效,并根据不同条件,分别逐步转变成终态相FeOOH和Fe_3O_4等。合金中含有Ni,Cr可以抑制早期中间态相的形成,但Ni,Cr却会促使后期于局部地区形成另一些中间态相。因此含Ni,Cr低合金钢虽早期在一般腐蚀方面具有较好的抗蚀性,但在后期在局部腐蚀方面则会导致耐蚀性大大降低。根据穆斯堡尔谱学和腐蚀电化学,作者阐明了合金元素的作用,澄清了某些看法并初步提出发展和评定耐海水腐蚀低合金钢的途径。
The potentiostatic anodic polarization of low alloyed steel in 3.5% NaCl can simulate the electrochemical processes at various micro-regions during corrosion in seawater. With this acceleration method, the relative content of intermediates that occur on each micro-zone can be increased. The authors detected these trace intermediates using the Mössbauer effect, thus grasping the phase composition of the barrier rust on the sample in seawater, which is not yet directly determinable. The results show that different low-alloy steels have different barrier rust phase compositions, except for the β-, γ-FeOOH end-phases which are possessed by the seawater samples and have different compositions respectively Microcrystalline or amorphous Intermediate rust similar to green rust I, Fe 2 (OH) 3 Cl, etc. These intermediate state rust easily oxidized in the air, dehydration, aging, and under different conditions, were gradually transformed into the final phase of FeOOH and Fe_3O_4 and so on. The alloy contains Ni, Cr can inhibit the formation of the early intermediate phase, but Ni, Cr will prompt the formation of other intermediate phase in some areas later. Therefore, Ni-Cr and Cr-low alloy steels have good corrosion resistance in general corrosion early, but corrosion resistance will be greatly reduced in the later stage of local corrosion. Based on Mossbauer spectroscopy and electrochemical corrosion, the authors elucidated the role of alloying elements, clarified some observations and initially proposed ways to develop and evaluate seawater resistant low alloy steels.