Corrosivity Evaluation of Copper-Nickel Alloy (90/10) in Pumps Used in Offshore Platforms for Seawater Pumping

Abstract

This work discusses the case of corrosion in a copper-nickel alloy used in seawater, where chlorination is necessary to control micro- and macro-organism growth that can render inoperable the seawater supply system used in an offshore platform. Studies developed in the last 30 years have shown copper-nickel’s adequateness in seawater, with a corrosion rate of about 0.001mm/year. However, annual equipment inspection showed localized corrosion in an internal chamber in a stand-by pump. Such corrosion occurred due to high-concentration of sodium hypochlorite (NaClO) injection into the operational system, even for pumps that were out of operation. To evaluate this corrosive process, gravimetric (mass loss) and electrochemical tests were developed in synthetic seawater with NaClO at concentrations of 100, 500, 1000 and 5000mg/L. The results indicated that the corrosiveness varied from low to moderate. The presence of pitting and crevices observed in the laboratory tests derails or compromises material use in seawater. It was concluded that there is a need for continuous monitoring of the NaClO injection in seawater pumps, and a method was proposed in order to minimize or avoid a high concentration of chlorine in standby pumps.

Microstructure, Mechanical and Corrosion Properties of Copper-Nickel 90/10 Alloy Produced by CMT-WAAM Method

“…The average corrosion rate determined based on the formula from the ASTM G59-97 standard and electrochemical measurement data is approximately 7.4 × 10 −5 mm/year. Based on the data obtained regarding the corrosion rate, the analyzed material can be classified based on the literature data [ 34 ] as low corrosion (below 0.025 mm/year) whereby the material is practically non-corrosive or the corrosion is very slow. Most works in the literature focused on the study of the corrosion properties of Cu-Ni 90/10 alloys [ 22 , 23 , 26 , 27 , 31 , 32 ] presenting electrochemical measurements carried out in the environment of a NaCl solution with a concentration of 1 to 3.5% or seawater solutions with additional chemical components [ 21 , 24 , 25 , 28 ]; therefore, it is difficult to directly compare the obtained results.…”

Challenges in the Numerical Analysis of Centrifugal Pumps¨: Energetic, Cavitation and Dynamic Characteristics

“…In some cases, it was necessary to analyze specific properties that are rarely discussed in the literature. One such example is the consideration of wall roughness, which may be due to different influences in the operation of the pumps [4]. To the best of our knowledge, there is no literature relevant to the link between roughness and the use of a suitable turbulent model with a proper computational grid.…”