No abstract

No abstract

Electrochemical techniques for the assessment of porosity in electrodeposited metal coatings are reviewed. The determination of porosity and corrosion, resistance is illustrated by electrochemical data from three coating/ substrate systems namely: electroless nickel on aluminium and steel and immersed gold coatings on an electroless copper-plated ABS polymer. Nickel coatings were up to 24 μm thick while gold deposits had thickness between 75 and 190 nm. Tafel extrapolation and linear polarisation resistance methods were used to determine the corrosion rate of the coated substrates. The aluminium samples were tested in 5% w/v (0.85 mol dm − 3 ) NaCl, while coated steel and ABS samples were immersed in 0.125 mol dm − 3 H 2 SO 4 and 0.1 mol dm − 3 NaBH 4 , respectively, at 295 K. Current vs. time curves and anodic polarisation behaviour have also been considered.

The cathodic polarisation behaviour of CA 104 nickel aluminium bronze (NAB) has been examined in fully characterised seawaters (filtered and artificial) using the rotating disc electrode (RDE) and the rotating cylinder electrode (RCE). Linear sweep voltammetry and a potential step, current transient technique were used to examine the charge transfer and mass transfer controlled cathodic response as a function of both laminar and turbulent fluid flow. For freshly polished surfaces, the rate of irreversible charge transfer controlled oxygen reduction is controlled by the exchange of a single electron and hydrogen evolution is only significant at potentials more negative than approximately )1.0 V vs. the saturated calomel electrode (SCE).

No abstract