4-dimensional digital inline holography of pitting corrosion of metal alloys

许多对环境和经济具有重要意义的化学反应发生在固体和气体或液体之间的界面上。其中一些反应会产生负面后果，例如腐蚀材料。这项研究计划将集中在金属合金的破坏性点蚀，特别是不锈钢和铝合金。这些合金设计为耐腐蚀，通常由氧化层保护。然而，在某些情况下，它们会受到局部点蚀的影响，这可能会导致问题。大约30%的化工厂故障与这种形式的腐蚀直接相关，造成了巨大的损失。为了更好地研究点蚀的最初步骤，我采用了椭圆显微镜表面成像(EMSI)技术，这是我的团队早些时候开发的一项技术，能够监测液体。我们现在可以测量不锈钢和其他合金上亚稳态点蚀事件周围保护性氧化层的厚度变化。与理论界合作，将进一步发展和分析这种腐蚀现象的新的数学模型。在这个项目中，我们建议应用一种新的方法，数字直列全息术(DIH)，与EMSI和对比度增强光学显微镜同时应用于对从腐蚀表面抛射出的颗粒进行成像。DIH将样品前面的完整体积表示为一张单独的图像，即全息图。数学算法可以重建成像体积内粒子的三维表示。这将有助于理解在点蚀过程中发生的初始过程。他说，这些研究的长期目标将是寻找表面活性剂，即使是极少量的表面活性剂也能够抑制点蚀的开始。减少腐蚀可能会产生巨大的经济和环境后果。

Many environmentally and economically important chemical reactions take place on surfaces at the interface between solids and gases or liquids. Some of these reactions have negative consequences, e.g. corrosion of materials. This research program will be focusing on the devastating pitting corrosion of metal alloys, specifically stainless steels and aluminum alloys. These alloys are designed to be corrosion resistant and are normally protected by an oxide layer. Nevertheless under some conditions they are affected by localized pitting corrosion, which can cause problems. About 30% of chemical plant failures are directly correlated to this form of corrosion at tremendous costs.           To study the initial steps of pitting corrosion, I adapted Ellipso-Microscopy for Surface Imaging (EMSI), a technique my group had developed earlier, to be able to monitor liquid phases. We can now measure thickness changes of the protective oxide layer surrounding metastable pitting events on stainless steels and other alloys. In collaboration with theoreticians, a new mathematical model of such corrosion phenomena will be further developed and analyzed.           In this project, we propose to apply a new method, Digital Inline Holography (DIH), simultaneously with EMSI and contrast enhanced optical microscopy to image particles ejected from a corroding surface. DIH represents the complete volume in front of the sample into one single image, the hologram. Mathematical algorithms can reconstruct a 3-dimentional presentation of particles within the imaged volume. This will help to understand the initial processes occurring during pitting corrosion.           The long-term aim of these studies will be to find surfactants, which, even in diminutive quantities are capable of suppressing the onset of pitting corrosion. Reducing corrosion could have enormous economical and environmental consequences.