The corrosion behaviours of 460 low alloy steels were investigated by the field exposure corrosion experiments with various long periods and 1200-3000 m depths in the natural deep-sea environment. XRD analysis results indicate that corrosion products of β-FeOOH, γ-FeOOH and Fe 3 O 4 increase and the corrosion product of α-FeOOH decreases with the exposure sea depth extending. Electrochemical experiment results reveal the corrosion status is aggravated with the exposure sea depth extending: corrosion potentials shift negatively to a minimum self-corrosion potential of −0.590 V (vs. SCE) and charge transfer resistances decrease to a minimum of 278 Ω cm 2 . Corrosion behaviours analysis shows that the average corrosion rate decreases with the time increasing and reaches a maximum value of 101 μm a −1 . The maximum pitting depth varies between 63.0 μm and 138 μm. Gray relational analysis shows that the corrosion rate of 460 steel is most influenced by the pressure and dissolved oxygen concentration of deep sea, exhibiting a positive correlation relationship.
The electrochemical migration (ECM) behavior of copper-clad laminate (PCB-Cu) and electroless nickel/immersion gold printed circuit boards (PCB-ENIG) under thin electrolyte layers of different thicknesses containing 0.1 M Na2SO4 was studied. Results showed that, under the bias voltage of 12 V, the reverse migration of ions occurred. For PCB-Cu, both copper dendrites and sulfate precipitates were found on the surface of FR-4 (board material) between two plates. Moreover, the Cu dendrite was produced between the two plates and migrated toward cathode. Compared to PCB-Cu, PCB-ENIG exhibited a higher tendency of ECM failure and suffered from seriously short circuit failure under high relative humidity (RH) environment. SKP results demonstrated that surface potentials of the anode plates were greater than those of the cathode plates, and those potentials of the two plates exhibited a descending trend as the RH increased. At the end of the paper, an electrochemical migration corrosion failure model of PCB was proposed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.