Prediction of Tube-Tubesheet Galvanic Corrosion Using Finite Element and Wagner Number Analyses

Abstract

Galvanic corrosion predictions for heat exchanger tube/tubesheet galvanic couples are presented and discussed. The predictions were performed using finite element analysis using two programs, WECAN and MARC, and by Wagner number analysis under conditions of secondary and tertiary current distribution. Long-term electrochemical potentiostatic polarization data generated over 120 days in natural seawater were used to account for time effects. Results of the predictions are presented in the form of potential and galvanic current density as a function of distance from the tubesheet along the tube axis. Seawater exposures of some tube/tubesheet material combinations were performed to compare with the predictions. These exposures used segmented tubes connected in series through the use of zero resistance ammeters. Material combinations exposed included a Monel Alloy 400 tubesheet coupled to a 90-10 copper-nickel tube, a 90-10 copper-nickel tube coupled to a zinc anode at the position of the tubesheet, and a nickel-aluminum-bronze tubesheet coupled to an Alloy 625 tube. Tube/tubesheet data obtained from the literature were also compared to predictions. This study is directed towards determining not only the degree of accuracy of the predictions from the finite element and Wagner number analysis techniques, but also the sensitivity of the analyses to small changes in the electrochemical data used to obtain the predictions. The feasibility of these two analysis techniques for accurate qualitative as well as quantitative galvanic corrosion prediction for the tube/tubesheet configuration is discussed.

Numerical Simulation of Galvanic Corrosion between Carbon Steel and Low Alloy Steel in a Bolted Joint

“…Finite element analysis (FEA) of potential and current distributions in galvanic systems has long been studied in the literature [21][22][23][24][25][26][27]. Such studies are often carried out to investigate fundamental effects of electrolyte geometry [26,28,29], electrode kinetics [25], and unique part geometries [21].…”

“…Such studies are often carried out to investigate fundamental effects of electrolyte geometry [26,28,29], electrode kinetics [25], and unique part geometries [21]. Early modeling attempts have provided an analytical solution [26,30] for the galvanic current and potential distribution around a galvanic junction involving two dissimilar metals kept side by side and covered by a corroding solution.…”

Corrosion Potential Profile Simulation in a Tube under Cathodic Protection

“…It is usual to find carbon steel boxes and titanium, stainless steel, or even different copper alloy tubes and plates [2]. All these alloys have different electrochemical corrosion characteristics, and due to their electrical contact a galvanic corrosion can be induced [3]. In the event of cathodic protection, applied in the box, the plate is cathodically polarized, but its effect may not be seen by the entire tube and a part of it will work as an anode.…”

Boundary element method predictions of the influence of the electrolyte on the galvanic corrosion of AZ91D coupled to steel

“…The influence of the electrolyte involves many factors such as pH, composition, concentration of the ions and the conductivity of the electrolyte. The influence of conductivity on galvanic corrosion has been studied in terms of "macroscopic" and "microscopic" galvanic cells [14], or in terms of the Wagner number [15,16]. Recent research revealed the complicated "alkalization", "passivation" and "poisoning" effects during the salt spray exposure which may be difficult to predict accurately using numerical methods [3].…”