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Surface composites are developed on Mg RZ 5 alloy by friction stir processing. During FSP, hard reinforcements are introduced into the matrix of RZ 5 alloy and dispersed uniformly by mechanical stirring action. The reinforcements dispersed were boron carbide, carbon nanotubes (multi-walled) and an 80:20 mixture of zirconia and alumina particles. Dynamic recrystallization and grain boundary pinning action by reinforcement particles resulted in the generation of fine-grained surface composites. Corrosion characteristics of the base material and the surface composites are studied by potentiodynamic polarization technique. The corrosion rates estimated for the surface composites are found to be far lesser than the base material while their polarization resistances were higher than the base material. Among all surface composites, B₄C particle reinforced surface composites exhibited the lowest corrosion rate of $\sim$15 mpy. Reduction in the corrosion rate of the surface composites is influenced by fine-grained microstructure and presence of harder reinforcement particles.

A functionalized epoxy resin (DGEBA) was synthesized from abietic acid, through the esterification and condensation reactions between the carboxyl groups of abietic acid and the basic functional groups of an epoxy resin. This method of synthesis increases the epoxy resin surface adhesion, as well as the chemical and thermal stability, for being used as a protective coating against corrosion of copper plates. Characterization analyses included FTIR and SEM of both raw and functionalized epoxy resin substrates performed. The corrosion performance of these coatings when applied onto Cu and stainless plates was tested in terms of: (i) immersion in a misty saline chamber, under accelerated corrosive conditions; (ii) Taber abrasion and (iii) hardness, adhesion and potentiodynamic polarization. The obtained results indicate the existence of a chemical bond between the epoxy ring and the carboxyl functional groups of abietic acid. This chemical bonding provided an increased adhesion as well as better chemical and thermal stabilities than those of the original resin. The corrosion resistance lining the functionalized epoxy resin films indicated that their anticorrosive efficiency was up to 30% higher than that of the functionalized resin.

Measuring the corrosion rate of a corroding metal is of interest in many situations including monitoring industrial processes and fundamental research in laboratories. The corrosion rate of a metal can be measured electrochemically by determining its polarization resistance, which is inversely proportional to the corrosion rate. What is introduced in this letter is a novel technique for extracting polarization resistance from electrochemical noise (EN) data. An advantage of this approach is that very short time records, of the order of a few seconds, can be assessed to see if they reveal a polarization resistance. The theoretical framework for this approach is based on a time-domain analysis of an electrical circuit model of an EN experimental arrangement. The analysis indicates that polarization resistance can be interpreted only if one electrode, not both electrodes, is predomi-nately generating electrochemical transients during a given time record. An algorithm for extracting polarization resistance from EN measurements is described and examples of its implementation on EN data support the features of the theoretical framework.

Electrochemical corrosion processes can be investigated by observation of charge flows between the electrolyte and the corroding metal. Usually, the charge flows are observed as spontaneous current and voltage fluctuations (electrochemical noise) in a three-electrode setup. Different types of corrosion processes can be recognized by electrochemical noise analysis. Uniform corrosion rate can be evaluated by estimation of polarization resistance between the metal and electrolyte. Local corrosion events (breakdowns of the passive layer) that produce characteristic transients observed in noise can be detected as well. Different methods of electrochemical noise analysis are presented in a brief review. The limitations and advantages of the proposed methods for corrosion monitoring and research are underlined. The experimental results are also discussed.

Electrochemical corrosion processes can be investigated by observation of charge flows between the electrolyte and the corroding metal. Usually, the charge flows are observed as spontaneous current and voltage fluctuations (electrochemical noise) in a three electrode setup. Different types of corrosion processes can be recognized by electrochemical noise analysis. Uniform corrosion rate can be evaluated by estimation of polarization resistance between the metal and electrolyte. Local corrosion events (breakdowns of the passive layer) that produce characteristic transients observed in noise can be detected as well. Different methods of electrochemical noise analysis are presented in a brief review. The limitations and advantages of the proposed methods for corrosion monitoring and research are underlined. The experimental results are also discussed.