Understanding the corrosion resistance, microorganism suppression and real-world weatherability and application potentiality of intrinsically hydrophobic polydimethylsiloxane (PDMS) coating is of great significance for developing multi-functional composite protective materials. In this paper, a pure PDMS coating was prepared through spray-coating technique on Q235 carbon steel. The surface morphologies, wettability, chemical compositions, corrosion resistance, bacteria adhesion and real-world atmospheric durability behaviors were investigated. The electrochemical assessment results show that the PDMS-coated Q235 carbon steel exhibits greatly enhanced charge transfer resistance (R ct), positive movement of corrosion potential (E corr), and extremely low corrosion current density (I corr). Besides, the PDMS coating presents high anti-bacterial efficiency against Escherichia coli and Pseudomonas sp. adhesion. The real-world atmospheric weatherability, salt spray and abrasion resistance reveal that the PDMS coating can be considered as a superior and durable barrier against marine corrosion and biofouling invasion.