Abstract: The inhibitive action of some aldehydes towards the corrosion of Al-3Mg alloy in 2M hydrochloric acid solution has been invedigated using polarization and weight loss measurements. The two methods give the same order of inhibition effeciency Polarization Studies reveal that cathodic polarization is more pronounced than anodic one. The results indicate that all the compounds Studied are excellent corrosion inhibitors and the percentage efficiency varying with both the type and concentration of the inhibitor and being in the following order: p-methoxy-benzaldehyde (1)>benzaldehyde (2)>p-chlorobenzaldehyde (3)> p-nitrobenzaldehyde (4). The degree of surface coverage of the adsorbed additives was determined and the results obey the Langmuir isotherm.Effect of temperature on the corrosion rate in absence and prance of different concentrations of the used inhibitors was investigated using weight loss measurements. The results indicate that the corrosion rate rapidly increases with increasing temperature. Arrhenius parameters have been calculated and discussed.