We report on a long-run evolution of electrical conductivity sigma (77 K) of n-Hg1-xCdxTe (x = 0.21) samples which were created by reactive ion-etching process (RIE) in hydrogen and argon plasma. We show that after storing at room temperature a(77 K) decreases to less than one half of its initial value in a time interval similar to 2 x 10(5) s. The time of the relaxation is about 1000 times longer than the etching time. The increase of the storing temperature to 323 K results to about 5 times faster rate. In the coincidence with our previous model we interpret the effects as a result of release and diffusion out of donor-like mercury interstitials (Hg-I) captured on defects inside the sample during RIE. The numerical solution of the diffusion equation allows to estimate the diffusion constant of Hg at room temperature > 10(-8) cm(2) s(-1) concentrations of two trap levels similar to 10(16) and 10(15) cm(-3) and respective formation free energies similar to -500 and similar to -600 meV. The traps are interpreted as complexes which are formed by extrinsic acceptors and bound Hg interstitials. The method is proposed to be a proper tool to study the defect structure also in other semiconductors.