Composites are often employed as repair materials for steel pipelines in the oil industry. Nevertheless, it is known that polymer matrix composites age through service life due to exposure to environmental factors, leading to a decrease in the durability of these repairs. In this work, alterations in glass fiber–epoxy composites aged for 1440, 2880, and 4320 h were studied in two different aging conditions: an accelerated aging chamber (with alternate cycles of exposure to ultraviolet [UV] radiation and water condensation) and immersed in salt water. The effects of aging in the material were evaluated by Fourier‐transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), lap‐shear tests, permeability analysis, and scanning electron microscopy (SEM) and in terms of mass variation. The results show that chemical changes, as well as alterations in mass and fiber exposure, increases in glass transition temperature and permeability, and more pronounced debonding composite/metal after lap‐shear tests, as compared to unaged materials, occurred. In general, the cycles of UV and water condensation were found to be more harmful to the material than aging in salt water, for the same exposure period.