Lee Hsun Lecture Series

Topic: Corrosion Inhibitors and Flow Induced Localized Corrosion – Achievements and Challenges

Speaker: Prof. Guenter Schmitt

Abstract:

In many industries the application of corrosion inhibitors is vital for failure prevention. Although added only in tiny concentrations they can provide enormous protection effects. This is explained by heterogeneous interface/interphase processes (physisorption, chemisorption), in which inhibitor molecules interact with surface atoms and by that reduce the rate of corrosion reactions. However, it was found recently that corrosion inhibitors can act not only by adsorption, but also by influencing the flow dynamic properties of liquids, thus decreasing the friction (wall shear stress) between solid surfaces and flowing media, which reduces the risk of flow induced localized corrosion (FILC) and increases the critical wall shear stress for the initiation of FILC. In systems which form protective films or scales FILC is initiated by a crack/spall mechanism of the protective scale. However, it became obvious that wall shear stresses encountered in technical flow systems are orders of magnitude too small to provide the fracture stresses needed to crack protective scales hydrodynamically. The newly developed “Freak Energy” approach offers a solution for this problem. It assumes that high-energy near-wall turbulence elements create freak events which impinge the surface vertically with forces higher than the fracture stress. It was proved that corrosion inhibitors can reduce the impact energy of such freak events significantly below the fracture stress of scales thus preventing initiation of FILC. Mechanistically this is explained by flow-induced concentration of inhibitor molecules in or near the viscous sublayer of the turbulent boundary layer causing a damping effect for impinging near-wall turbulence elements. The lecture discusses the achievements and challenges in FILC inhibition.

Prof. Guenter Schmitt graduated from the Cologne University and Aachen University of Technology inGermany with a Diploma and Ph.D. in Chemistry. In 1986 to 2007, he was a Professorfor Corrosion Protection Engineering and Head of the Laboratory for Corrosion Protection at theIserlohn University of Applied Sciences. Additionally since 2005 CEO and mainshareholder of the Institute for Maintenance and Corrosion Protection Technologies (IFINKOR)n.p.Ltd., Iserlohn, Germany.

His groups are working on subjects in the field of corrosion, corrosion protection and surfacemodification. Special fields of R&D include corrosion and corrosion protection in production,transport and processing of fossil fuels(oil, gas, coal), sweet and sour gas corrosion, inhibition, organiccoatings, electroless alloy plating, temporary corrosion protection, hydrogen induced corrosion, flowinfluencedcorrosion, interface/interphase phenomena, and electrochemistry. He was also involved inresearch on chemical processes for organic and metalorganic intermediate chemicals (e.g. synthesis ofspecial chemicals and polymer precursors, homogeneous catalysis). His R&D work is documented inmore than 320 publications, more than 60 invited lectures.

He has received the Fellow of NACE international (2005), European Corrosion Medal from the European Federation of Corrosion (2011), etc.

Prof. Guenter Schmitt is actively involved in corrosion technology worldwide, such as Co-Founder, Past President (1995-2004) and Honorary Member (2006) of the German Society forCorrosion Protection (GfKORR); Scientific Chairman of EUROCOR'99; Principle author of WCO White Paper (May 2009) "Global Needs for Knowledge Dissemination,Research, and Development in Materials Deterioration and Corrosion Control"; He was elected as Vice Chairman of the International Corrosion Council (2015-2017), Chairman of the InternationalCorrosion Council 2018-2020.