In this study, the corrosion mechanism of an Al-Cu-Li alloy manufactured by two different treatment routes (T3 and T851) was evaluated by immersion and electrochemical tests in solutions containing chloride ions (Cl-). For both alloys, the formation of cavities on the surface was associated with micrometer-sized intermetallics (IM’s), however, in addition to this attack, the alloy submitted to T851 treatment also presented an attack called severe localized corrosion (SLC), caused by the preferential attack to the nanometric T1 (Al2CuLi) phase. The electrochemical concepts involved in these two types of attacks were discussed. During the IM’s corrosive process, whereas the O2 reduction occurred over the IM’s, the Al dissolution is favored around the particle, forming trenching and cavities (with 2 and 6 μm of depth). On the other hand, the mechanism associated with the SLC is related to the formation of a differential aeration cell followed by the evolution of H2, with greater depth of attack penetration (8 and 35 μm). Additionally, by the use of the Scanning Vibrating Electrode Technique (SVET), it was concluded that the higher anodic currents observed for the T851 temper were related to the relation between the anodic area (Aa) and the cathodic area (Ac).

Corrosion is still one of the most serious and frequent problems in industries. The phenomena involved in the corrosion mechanism of Al-alloys may be explained by formation of galvanic cells between the metal matrix and heterogeneities, such as precipitates, intermetallic phases leading to potential differences and electrochemical reactions. In the cathodic sites, the main reactions are oxygen reduction reaction, in aerated neutral environments, and hydrogen evolution in acid media. This last type of reaction might also occur in neutral solutions inside pits (anodic region). In this study, the mechanism of hydrogen evolution during corrosion of the 2198-T8 Al-Cu-Li alloy exposed in a chloride solution was investigated. The mechanism was related to the presence of T1 phase (Al2CuLi), which is the main strengthening phase in this material. This phase is highly active and, when exposed to corrosive media, leads to severe localized corrosion (SLC). One of the main characteristics related to SLC is hydrogen gas evolution which was confirmed by gel visualization. In this study, the hydrogen evolution mechanism inside the SLC sites was studied by scanning electrochemical microscopy (SECM).

O objetivo deste estudo foi investigar se existe associação entre a síndrome da dor patelofemoral e as medidas clínicas estáticas: os ângulos do retropé e Q. Foi realizado um estudo observacional, transversal, caso-controle, no qual foram avaliados 77 adultos (ambos os sexos), 30 participantes com síndrome da dor patelofemoral e 47 controles. Foram medidos os ângulos do retropé e Q, por meio da fotogrametria. Testes t para amostras independentes foram usados para comparações dos resultados das variáveis contínuas entre os grupos. Os resultados das variáveis contínuas foram transformados em classificações clínicas categóricas, para verificar a associação estatística com a disfunção, e o teste do χ2 para respostas múltiplas também foi utilizado. Não houve diferença entre os grupos para o ângulo do retropé [média da diferença: 0,2º (IC95% -1,4-1,8)] e ângulo Q [média da diferença: -0,3º (IC95%-3,0-2,4). Não houve associação entre o ângulo do retropé [Odds Ratio: 1,29 (IC95% 0,51-3,25)], assim como entre o ângulo Q [Odds Ratio: 0.77 (IC95% 0,31-1,93)] e a ocorrência da síndrome da dor patelofemoral. Apesar de serem teoricamente justificadas e amplamente utilizadas na prática clínica fisioterapêutica, não pode-se afirmar que as medidas dos ângulos do retropé e Q, quando mensuradas em posição ortostática, estão associadas com a ocorrência da síndrome da dor patelofemoral. Essas medidas podem ter aplicabilidade limitada na triagem desta disfunção.

The aim of the present study was to investigate the association between the patellofemoral pain syndrome and the clinical static measurements: the rearfoot and the Q angles. The design was a cross-sectional, observational, case-control study. We evaluated 77 adults (both genders), 30 participants with patellofemoral pain syndrome, and 47 controls. We measured the rearfoot and Q angles by photogrammetry. Independent t-tests were used to compare outcome continuous measures between groups. Outcome continuous data were also transformed into categorical clinical classifications, in order to verify their statistical association with the dysfunction, and χ2 tests for multiple responses were used. There were no differences between groups for rearfoot angle [mean differences: 0.2º (95%CI -1.4-1.8)] and Q angle [mean differences: -0.3º (95%CI -3.0-2.4). No associations were found between increased rearfoot valgus [Odds Ratio: 1.29 (95%CI 0.51-3.25)], as well as increased Q angle [Odds Ratio: 0.77 (95%CI 0.31-1.93)] and the patellofemoral pain syndrome occurrence. Although widely used in clinical practice and theoretically thought, it cannot be affirmed that increased rearfoot valgus and increased Q angle, when statically measured in relaxed stance, are associated with patellofemoral pain syndrome (PFPS). These measures may have limited applicability in screening of the PFPS development.