  We present a new method for the approximate solution of the strongly coupled,
nonlinear stress-diffusion problem that appears when modeling hydrogen
transport in metals. The most salient feature of the proposed approximation is
that it is fully variational, meaning that all the discrete equations are
obtained from the optimality conditions of an incremental potential, even for
inelastic mechanical behavior. Like other variational methods, the proposed
algorithm has remarkable properties, including the symmetry of the tangent
operator, making its solution extremely efficient compared to other similar
methods available in the literature.
