On site galvanostatic passivation of stainless steel tanks

Abstract

The PIPE phase 2 project aims to building a customized system for galvanostatic passivation in field conditions and to optimize the surface treatment parameters. The PIPE phase 1 results have demonstrated solid milestones in the bench and the small-scale tests, and the scientific challenges are related to the integration of all system for an adequate field performance. The galvanostatic passivation core components are the counter-electrode and the electrolyte spraying system, since it needs to guarantee the surface humidity during the treatment time. The electrochemical impedance spectroscopy (EIS) was considered as the technique to qualify the passivate surface in on-site conditions and there are a lot of challenging aspects to be faced. The on-site EIS was developed during the PIPE phase 1, nevertheless, it is required to develop a deep study including differents surfaces / conditions in order to define an acceptance criterion. The EIS is going to be combined with the x-ray photoelectron spectroscopy (XPS) technique in order to assess the oxide passive film properties such as chemical composition, Cr:Fe ratio, thickness and corrosion resistance. Also, the XPS technique is a double check measurement for the EIS results, and it helps to qualify the on-site EIS for field applications. The ASME BPE code define that the chromium and iron ratio (Cr:Fe) needs to be up from 1.3:1 in order to approve the passivated surface. It is expected to reach a close relation among the EIS and XPS measurements in terms of passive film properties and, based on that, XPS results is going to qualify on-site EIS measurements. The galvanostatic passivation of stainless steel tanks inner surface is the core for the technique to be developed, and it is quite useful to corrosion resistance and biological contamination in life science and food grade sectors and their utilities. The business regarding the technology is going to be provided as engineering and surface treatment services. It is important to highlight that there is no competitor in this specialization in the market and as a consequence it is expected a big demand for the service. (AU)