A growing number of new and innovative applications of Mg alloys is observed recently due to unique weightstrength ratio. Unfortunately, magnesium has also a number of undesirable properties including poor corrosion resistance. Therefore a development of more durable protective systems is concerned as the challenge. The main problem results from the fact that mechanism of corrosion of Mg alloys varies with a kind of alloy, impurities from mechanical processing, environment and from potential applications. Frequently, corrosion process contains complex steps of phenomena that overlap each other (general, pitting, bimetallic, filiform types of corrosion). There are two main kinds of surface engineering techniques that modify surface properties: physical or chemical treatment. Based on the own results a review of selected technologies was made taking into consideration improvement of corrosion resistance as the priority. The example of the first group of methods, high-energy beam surface melting of magnesium alloys, produces surface layers with a fine microstructure of significantly reduced dimensions of intermetallic precipitates. A resistance to general corrosion was improved as a result of this surface treatment for AZ91, AZ31 tested alloys. The susceptibility to pitting corrosion in terms of Epit value was not improved. Indications to improve pitting resistance are discussed. Better results in terms of resistance to local corrosion were obtained after chemical surface treatment based on phosphate/permanganate process. Taking into account conversion coatings as a sub-layer for an organic coating, some examples of the phosphating process in comparison with sol-gel applied coating are shown. In both cases an optimization of technological parameters is required, however, even for the time being corrosion resistance obtained is satisfactory. Since Mg alloys are considering as a material of increasing use in automotive industry, electroplating of zinc coatings is taken into account. The possibility of formation of uniform and relatively dense zinc coating was confirmed for AZ31 alloy, only. A consecutive process is elaborated by two-step electrodeposition. The first from alkaline bath is followed by the second step in acidic chloride bath. A dense and compact complex layer is obtained. The durability evaluated by electrochemical methods increases about three times in comparison with a single coat obtained from alkaline bath. Further increase of corrosion resistance by a chemical post-treatment is indicated. Despite the fact that in many examples mentioned above a significant corrosion protection of Mg substrate is achieved a serious corrosion problem starts for the case of mechanical defect exposing Mg substrate. Using polymeric coatings containing special substances as corrosion inhibitors selectively leached from the coating at defect to the substrate/electrolyte interface, as the future approach is discussed.

The pitting corrosion of copper in both LiBr and NaBr solutions has been studied using potentiodynamic measurements and surface analysis techniques. It was found that pitting of Cu was evident only after the formation of a protective film of CuO and/or Cu(OH)2, depending on the bromide content. In case of NaBr the hysteresis loop of pitting corrosion started to appear at 3.1·10-2 M while in case of LiBr it started at 7.4·10-2 M bromide content. These results, together with the current – time trend and the surface analysis, confirm the role of Li+ on the passivation and pitting attack on copper metal.

Selected failures involving three corrosion protection systems i.e. hot dip galvanized zinc coatings and duplex systems, powder coatings and coating systems for steel tanks and bridges have been discussed.

The scope of work carried out at the Institute of Non-Ferrous Metals in Gliwice over the last ten years, related to the processing of zinc and lead, has been described. Results of hot-dip galvanizing of specimens made of reactive steel grades in baths composed of new zinc alloys with an addition of aluminium, nickel, manganese, tin and antimony are presented. The coatings obtained have been compared with those from batch and continuous galvanizing conducted in pure-zinc baths, with aluminium as the only additive. Analysis of the obtained results was made taking into account the most recent fi ndings on the mechanism of coating growth on qualitatively and quantitatively different steel substrates. The predominant role of the chemical composition of a bath has been emphasized. A universal coating was obtained at reasonably low zinc consumption, which was characterized by a favourable multi-layered structure (batch method) or a single-layered structure (continuous method), and it was aesthetic and of high quality independently of the grade of reactive steel subjected to galvanizing. As far as lead processing is concerned, a new technology for the fabrication of a series of lead alloys in industrial conditions, mainly for application in the production of batteries, has been developed. Moreover, possibilities of increasing the assortment of the alloys developed by more effective use of domestic raw materials, and of improving product quality, have been shown. Finally, new alloys for the coating of electric cables have been proposed.

Due to the number and variety of questions relating to the notion of corrosion, many aspects are taken into consideration when attempting to classify this phenomenon based on a given criterion. The paper attempts to systematise the complex concept of corrosion into a coherent whole. The aspect of hot-dip galvanizing of white and spheroidal malleable cast iron is presented and the kinetics of the growth of the diffusion layer are also shown.