Corrosion is a key issue for operators in the oil and gas industry since production fluids contain some water and both CO2 and H2S acid gases. In this context, this paper illustrates the development of a reactive barrier polymer against corrosion by H2S of offshore flexible pipes. The role of this reactive material, called anti-H2S material, is to avoid H2S reaching the structural steel layers of the flexible pipe during the whole service life of the structure, usually 20 years, and hence to place the steel layers in a sweet service environment. Placed between the existing pressure sheath and the steel layers, the anti-H2S material has the ability to neutralize H2S during its diffusion within the material. The neutralization is ensured by an irreversible chemical reaction on reactive components that are dispersed in the material. The raw material selection is based on both accurate requirements for their use in a flexible pipe and expected performances in a sour service environment over a long period of time. Some laboratory qualifications and experimental techniques are used to qualify the behavior of the material and build the material database. A dedicated multiphysics model is developed based on the coupling of permeation mechanisms and gas-solid reactions. Qualification of both the material and the model is performed thanks to middle-scale and full-scale tests conducted in representative sour service conditions.