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- Electrochemical assessment of corrosion-fatigue degradation stagesPublication . Simões, Alda Maria Pereira; Canut, Felipe; Reis, Luis; Napoleão Bastos, Ivan; Mamiya, EdgarABSTRACT: The study is focussed on the joint effect of corrosion and mechanical cyclic stresses observed on mooring chains of Floating Production Storage and Offloading (FPSO) units. The tests were performed using grade R4 steel in artificial sea water, under stress-controlled and fully reversed loading. The corrosion-fatigue degradation was monitored using open circuit potential measurements simultaneously with the cyclic mechanical load. The open circuit potential response varies during the corrosion-fatigue test, depending on the stage of degradation of the material. This technique has proven to be capable of identifying important phenomena, such as crack initiation and crack propagation, on the material under corrosion-fatigue loading condition.
- Naphthenic corrosion using electrochemical and analytical techniquesPublication . Simões, Alda Maria Pereira; Pereira Da Silva, Rejane Maria; Suffredini, Hugo; Santos, Luis; Bastos, Ivan NapoleãoABSTRACT: Naphthenic acid corrosion of steel was studied in a stagnant, biphasic oil/aqueous phase system, by means of electrochemical measurements and surface analysis. Corrosion was restricted to the region of the aqueous phase, as crater-shaped pits that eventually coalesced, generating a nearly uniform attack in the vicinity of the oil phase. In-situ electrochemical impedance spectroscopy (EIS) reveals the processes occurring at the aqueous phase, which nevertheless increase with the fraction of oil phase and with degree of acidity of the oil.