Electrochemical corrosion testing of boronized and unboronized steels

Boronizing is a thermo-chemical surface coating technique with which surface properties of materials are enhanced substantially. One of these properties is corrosion resistance. Corrosion resistance testing has been performed in many ways right from the traditional weight loss methods to the latest electrochemical techniques. These electrochemical techniques are more reliable and less time consuming and hence are widely accepted for corrosion testing in the industry. In the present work, direct current (D.C) corrosion testing studies of both boronized and unboronized steels have been discussed. Three types of steels, AISI 1018, AISI 4340 and AISI 304 stainless steel, were considered for this work. The steels were boronized and tested for corrosion resistance in the solutions 5% v/v HCl, 4% w/v NaCl, and 5% w/v KOH. These three solutions represent acidic, salt and basic media. Unboronized steels were also tested in these solutions. Linear Polarization, Tafel plots and Cyclic Polarization were the three techniques used to analyze the corrosion resistance of boronized and unboronized steels. Comparative studies revealed increase in corrosion resistance of AISI 1018 by 3-8 times, of AISI 4340 by 3-10 times, and of AISI 304 by 5-17 times. The results from Cyclic polarization experiments proved an increase in pitting resistance of the boronized specimens