Cathodic polarization enables SEM illustration of manganese biomineralization in natural biofilms

Fatigue crack growth rate was developed on three heats of alloy 718 (UNS N07718) under cathodic polarization, over a wide range of loading conditions. Fatigue crack growth rate increased with decreasing frequency over a range of Kmax and K conditions. In most cases, there was no evidence of a plateau in fatigue crack growth rate at low frequencies. The fatigue crack growth rate over the range of conditions evaluated were influenced by static crack growth rate at Kmax. The principle of superposition of fatigue crack growth and static crack growth was used to rationalize the observed crack growth rate response. Static crack growth rate of alloy 718 measured under constant K conditions, was lower than that measured under rising displacement conditions. A crack tip strain rate based model was used to rationalize the fatigue crack growth rate behavior and the static crack growth rate behavior under constant K. However, the formulation of the model for the rising K was not able to rationalize the crack growth rate under rising displacement conditions.

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An Automatic Polarization Apparatus for Electrochemical Corrosion Studies

CORROSION ◽

10.5006/0010-9312-25.12.515 ◽

1969 ◽

Vol 25 (12) ◽

pp. 515-519 ◽

Cited By ~ 9

Author(s):

W. D. HENRY ◽

B. E. WILDE

Keyword(s):

Cathodic Polarization ◽

Reference Electrode ◽

Electrochemical Corrosion ◽

304 Stainless Steel ◽

Constant Current ◽

Voltage Source ◽

Potential Range ◽

Alloy Development ◽

Corrosion Studies ◽

Potentiodynamic Anodic Polarization

Abstract Statistical alloy development programs in which electrochemical screening techniques are used require facilities to produce precision polarization data. Conventional equipment and techniques presently available for such programs are not entirely satisfactory. Therefore, modifications were made to readily available commercial equipment to significantly improve the attainable sensitivity and reproducibility. This paper describes in detail the procedures necessary to produce an apparatus that automatically measures and records anodic and cathodic polarization curves over an applied potential range of ±2.0 volts. Traverse rates between 2 × 10−3 and 3 × 104 volts per hour are attainable and can be used to polarize electrodes through zero volts (with respect to reference electrode) without the necessity of manual switching. A special mode switch is described in detail with which the basic electronic potentiostat can be used as a constant current or constant voltage source by manual selection. The results obtained from three typical polarization experiments: (1) potentiodynamic anodic polarization, (2) galvanodynamic cathodic polarization, and (3) galvanodynamic linear polarization of AISI Type 304 stainless steel in hydrogen saturated 1N H2SO4 at 25 C (77 F), showed the performance of the apparatus to be equal to or superior to that of conventional manual procedures.

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