On-site galvanostatic passivation of stainless steel tanks

Abstract

The aim of this R&D project is developing an optimized procedure of galvanostatic passivation to be performed in stainless steel tanks installed on industrial sites (on-site), including the development of the required devices. The national and international industrial sectors use stainless steel tanks for bioprocess and frequently they have financial injuries due to corrosion and biofilm degradation of these assets, and the traditional passivation treatments by immersion or aspersion of the electrolytes do not provide an enough corrosion resistant passive film. The galvanostatic passivation treatment generate a higher level of corrosion resistant to the surface than traditional passivation, however, it is limited to bench treatments and small areas. The scientific and technological challenge of this research project is related to become possible the on-site galvanostatic passivation treatment in large superficial areas, focused on internal surface of stainless steel tanks. This tec business will be offered to the market as a service provision of surface treatment, and it is important to highlight the high level of project originality whereas there is not a market player and anything similar publication such as article or patent. The first step of the methodology consists in optimize the treatment parameters: (i) electrolyte based in citric acid and addition of sodium nitrate, (ii) definition of current density and passivation time. The development of the treatment devices will take account that they need to attend large superficial areas in an on-site condition (target to phase 2 PIPE). A 316L stainless steel pilot tank with 1 m2 of area will be builted in order to allow the on-site galvanostatic passivation treatment tests. The passivation level of the surface will be characterized by on-site electrochemical techniques in order to assess the efficacy of the galvanostatic passivation treatment. The project methodology is considering an intensive use of portable electrochemical techniques and X-ray photoelectron spectroscopy (XPS), seeing that they are suggested by Bioprocessing Equipment Code ASME BPE to assess and qualify passivated surfaces. Other techniques such as atomic force microscopy, Raman spectroscopy and scanning electron microscopy complement the two main techniques. The desirable results are related to the development of the on-site galvanostatic passivation treatment procedure, the required devices to perform the on-site treatment and the specification of an electrolyte based on citric acid. The team consider that if this target would be reached then the tec business will be ready for the second phase of PIPE and to the industrial market. (AU)