**4. Conclusions**

Ion exchanged strengthening of borosilicate glass tubes was carried out under an electric field by using relatively short treatment times. The depth of the exchanged layer increases with the field intensity. Reversing the field polarization can modify the residual stress; moreover, the sequence of applying the fields with different polarizations is important to avoid the formation of cracks on the glass surface. Bending strength of samples treated by the double-reversed field is higher compared to those subjected to EF-IOX on one side or to conventional ion exchange.

Additional studies are required to find the effect of different parameters, such as salt and glass composition, treatment time and temperature, field intensity and other thermodynamic and electric factors on the assisted ion exchange process. The structural changes during the electric field should also be investigated. Nevertheless, the preliminary results obtained in the present work point out that electric field-assisted ion exchange can be employed for improving the mechanical properties by relatively short duration treatments.
