Corrosion mechanism and degradation behavior of basalt fiber-reinforced composites in sulfuric acid solution

Epoxy resins reinforced by basalt fibers were treated with a sulfuric acid solution for different periods and concentrations. The tensile strength of the composites was examined after the treatment. The fracture surfaces were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The tensile strengths of the sulfuric acid solution-treated samples showed a decreasing trend with treating times and concentrations. However, after 250–500 h of treatment time, the tensile strengths showed an increasing trend. Based on the experimental results, the possible corrosion mechanisms were explored. Sulfuric acid leads to insoluble sulfur oxide formation with high C, Ca and Fe element contents on the fiber surface. With the continuation of sulfuric acid reaction, a thin corrosion shell covers the whole fiber surface. The thickest corrosion shell caused a significant increase in the tensile strength at the breaking of basalt fibers.