DESIGN OF ION-IMPLANTED COATINGS TO IMPEDE HYDROGEN CONTAMINATION OF STEEL

The present work utilizes a recently proposed methodology for performi ng tests and analysing the data from electrochemical hydrogen permeati on experiments so as to characterize the effect of surface coating lay ers on hydrogen ingress into the sample. This methodology has been suc cessfully applied to nitrogen ion-implanted API-5L-X65 type pipeline s teel. Hydrogen permeation experiments were conducted using a double el ectrolytic cell, thermostatically controlled at 308 K, containing a 0. 1 N NaOH solution in both compartments. The hydrogen permeability beha viour of the low alloy high strength steel is significantly altered wh en it is coated with a nitrogen ion implanted layer. The implanted lay er was shown to possess an apparent hydrogen diffusivity much smaller than that of the substrate steel, while presenting an apparent hydroge n solubility considerably greater than that of the uncoated substrate.