Synthesis and characterization of a novel composite Nano-polymer corrosion inhibitor and its corrosion inhibition behavior and mechanism for J55 steel

A novel composite nanopolymer corrosion inhibitor was designed and synthesized to enhance the service life of J55 carbon steel used for oilfield casings. Its corrosion-inhibition performance and mechanism on J55 steel in a 3.5 wt% NaCl solution saturated with CO₂ were systematically investigated. The copolymer (PAMAA) was first synthesized using acrylamide (AM), acrylic acid(AA), and 2-acrylamido-2-methylpropanesulfonic acid(AMPS) as monomers. On this basis, nano‑zinc oxide (nano-ZnO) was introduced to prepare a new nano-ZnO/polymer composite (ZnO/PAMAA) via in situ polymerization. The corrosion inhibition performance in the corrosive medium was evaluated by weight-loss tests and electrochemical measurements. The adsorption behavior of the inhibitor on the carbon steel surface was analyzed via interface characterization, and the inhibition mechanism was further verified at the molecular level through theoretical simulation. The above content shows that the ZnO/PAMAA composite exhibits excellent corrosion inhibition of J55 steel in 3.5 wt% NaCl solution saturated with CO₂. FTIR and XRD results confirm the successful synthesis of the nano-ZnO/polymer composite ZnO/PAMAA. The observation results from the transmission electron microscope (TEM) and the test results from dynamic light scattering (DLS) both indicate that the modified nano-ZnO is uniformly dispersed in the polymer solution, without obvious agglomeration. Electrochemical experiments demonstrate its outstanding inhibition efficiency, with the inhibition efficiencies calculated from EIS and Tafel curves reaching 88.40% and 91.45%, respectively. A protective film is formed on the carbon steel surface, and the inhibition mechanism is further verified through interface characterization and theoretical simulation. It is concluded that the novel composite ZnO/PAMAA presents superior corrosion inhibition performance for J55 steel in 3.5 wt% NaCl solution saturated with CO₂. It primarily forms a stable protective film on the J55 steel surface, reducing the charge transfer rate and thereby achieving excellent corrosion inhibition efficiency.