  We propose a phenomenological field theoretical approach to the chemical
etching of a disordered-solid. The theory is based on a recently proposed
dynamical etching model. Through the introduction of a set of Langevin
equations for the model evolution, we are able to map the problem into a field
theory related to isotropic percolation. To the best of the authors knowledge,
it constitutes the first application of field theory to a problem of chemical
dynamics. By using this mapping, many of the etching process critical
properties are seen to be describable in terms of the percolation
renormalization group fixed point. The emerging field theory has the
peculiarity of being ``{\it self-organized}'', in the sense that without any
parameter fine-tuning, the system develops fractal properties up to certain
scale controlled solely by the volume, $V$, of the etching solution.
  In the limit $V \to \infty$ the upper cut-off goes to infinity and the system
becomes scale invariant. We present also a finite size scaling analysis and
discuss the relation of this particular etching mechanism with Gradient
Percolation.
  Finally, the possibility of considering this mechanism as a new generic path
to self-organized criticality is analyzed, with the characteristics of being
closely related to a real physical system and therefore more directly
accessible to experiments.
