Aqueous hydrogen sulphide corrosion of iron, iron/chromium and iron/nickle alloys.

Aqueous corrosion reactions, which are electrochemical, occur at the metal/liquid interphase. In anaerobic acidic environments the rate of corrosion is frequently controlled by a charge-transfer reaction rather than by the rate of diffusion of reactant to (or from) the interphase. These environmental conditions are common to the production and processing of sour oil and gas, as is the usage of ferrous based corrosion resistant alloys in which chromium and nickel are the predominant alloying additions. The rate of a charge-transfer reaction is determined by two fundamental parameters: the exchange current density and the transfer coefficient. They are related in the Butler-Volmer equation which has been referred to as the first law of electrode kinetics. These parameters have an equal significance when considering the rate of charge-transfer controlled corrosion processes, which frequently determine the service life of engineering artifacts. The difficulties associated with electrode kinetic methods, in this instance potentiodynamic polarization, are usually concerned with reproducibility. However, to gain meaningful kinetic data it is also necessary to account for the contribution to the measured potential of the electrical resistance of the electrolyte and concentration polarization. This work developed methodologies and techniques to investigate and evaluate the fundamental electrochemical parameters of reactions that occur during aqueous hydrogen sulphide corrosion. Linear regression analysis was used on selected ranges of the potentiodynamic polarization data to obtain values of the anodic and cathodic transfer coefficients for the corrosion reactions of 99.998% iron in aqueous solutions saturated with hydrogen sulphide. The same techniques were used to study the effects of chromium alloying additions, nickel alloying additions and the layer of corrosion products which formed on the surface of the working electrode. The finite supply of resources on the planet should be a motivating force to extend the service life of engineering artifacts. In the long term this could be achieved by using electrochemical data to aid in the design and use of corrosion resistant alloys. The experimentally-determined values of the anodic and cathodic transfer coefficients may be put to a more immediate use in the Stern-Geary equation to provide projections of corrosion rates from data gathered using linear polarization or AC impedance techniques.

Author dc:creator

• Nuttall, Robert Horan

Advisor dc:contributor.advisor

• D. Kirkwood, K.N. Strafford, A. Turnbull and L.J. Power

• Helicopter flight control
• Computational intelligence
• Inverse simulation
• Genetic algorithms
• Pilot modelling
• Multi-objective optimisation

Language dc:language

en

Identifier

oai:rgu-repository.worktribe.com:2807509
https://doi.org/10.48526/rgu-wt-2807509

OAI identifier oai:identifier

oai:rgu-repository.worktribe.com:2807509