X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), ion scattering spectroscopy (ISS) and secondary-ion-mass spectrometry (SIMS) have been used to examine the composition of the visible corrosion layer formed on a chloride-ion-selective electrode (ISE) during exposure to a simulant solution containing dissolved Halon fire suppression by-products such as HBr. ISS depth profiling indicates that the Cl- is replaced by Br- forming a corrosion layer about 75 A thick. Surface recovery of the ISE by aqueous hydrochloric acid etching has also been studied as a function of acid concentration and etchant contact time. Based on XPS data, the optimum etching parameters have been found to be 0.5 mol L-1 aqueous HCI and a contact time of 290 s. XPS, AES, ISS, and SIMS data indicate that the HCI etch removes most of the Br- in the near-surface region, thus providing an in situ means of regenerating chloride-ion-selective electrodes.