Advanced high-strength steels (AHSS), are commonly used in the manufacture of car bodies, as well as in front and rear rails, and safety posts. These components can be exposed to corrosive environments for instance, in countries where de-icing salts are used. In this work, the corrosion behavior of four AHSS steels with dual-phase [ferrite-martensite (DP) and ferrite-bainite (FB)] steels were studied by means of electrochemical noise (EN) measurements according to the ASTM G199-09 standard in NaCl, CaCl₂ and MgCl₂ aqueous solutions at room temperature. The direct current (DC) trend data from EN were removed by a polynomial method of statistical and spectral analysis. According to the noise resistance (R_n) values obtained for the DP and FB dual-phase steels, both the martensite/bainite content and morphology of the phase constituents have an important effect on the corrosion behavior of these steels. The L.I. (localization index) (0.00054 to 0.15431), skewness (−6.18 to 7.35) and kurtosis (high values 37.15, 74.84 and 106.52) were calculated. In general, the results indicated that the main corrosion process is related to uniform corrosion. Corrosion behavior of AHSS steels exposed in NaCl solution could be related to the morphology of the phase constituents exposed in NaCl, CaCl₂ and MgCl₂ solutions.

A series of oxidation tests were conducted for a nickel base superalloy, as these materials are used at high temperature in aggressive conditions, thus the influence of oxygen on their degradation mechanisms must be known. The material was treated for up to 150 h at 900 and 1000°C in a furnace able to control and maintain atmospheres with different partial oxygen pressures. The oxidation rate of the material was determined by gravimetric means. In all cases, the rate of oxidation followed parabolic regimes that depended on the value of oxygen partial pressure. The oxide scale formed was characterised by X-ray diffraction and scanning electron microscopy; these analyses revealed that the oxide scale consisted of an outer TiO₂ layer and inner Cr₂O₃ layer under all experimental conditions. Cross-section analyses indicated the development of internal oxidation and the presence of gamma-prime free zones.

A systematic variation of the parameters involved in the spot welding by electrical resistance of galvannealed strips was carried out on samples from a 2 mm thickness galvannealed high strength low alloy steel strip used for automotive applications. The varied parameters in the present study were welding current, welding time, holding time after welding and number of welding pulses, while the dimensions and characteristics of the electrodes and the applied force during welding were kept constant. The wear of the electrodes is important, however it was not the aim of the present study, therefore it was not taken into account. The experimental results were analysed to evaluate the influence of the various parameters on diverse characteristics of the welded bead. It was possible to determine the optimal operational conditions for this particular type of material.

A series of analyses were conducted on samples of an austenitic type 304 stainless steel that exhibited a high degree of sensitization (DOS) after being subjected to a solution annealing treatment at 1050°C. The DOS was detected by electrochemical potentiokinetic tests. Examination by scanning electron microscopy of etched samples revealed the presence of δ-ferrite within the austenitic matrix, and of the segregation of chromium and nickel in either phase; images obtained by atomic force microscopy revealed localized attack at the austenite/δ-ferrite interface. It was found that the DOS and the ferrite number of the steel were reduced as the material was held at the solution temperature for longer times. Aging at 650°C showed precipitation of chromium carbides at grain boundaries and at the austenite/δ-ferrite interface; this treatment increased the DOS.