Blockchain technology for Industrial IoT (IIoT) research explores how decentralized ledger systems can enhance security, reliability, and transparency in industrial networks where devices, machines, and sensors exchange massive volumes of operational data. Research papers in this area investigate applications such as secure machine-to-machine communication, tamper-proof data logging, decentralized device authentication, predictive maintenance, and supply chain traceability within industrial ecosystems. Studies highlight the use of smart contracts to automate industrial workflows, enforce operational rules, and manage transactions without intermediaries, while cryptographic techniques ensure data integrity and confidentiality. Key challenges addressed include scalability to handle high-frequency IIoT data, latency constraints for real-time operations, interoperability with legacy industrial systems, and resource limitations of edge devices. Proposed solutions often combine lightweight consensus protocols, hybrid blockchain architectures, and edge/fog integration to optimize performance and security. Overall, this research demonstrates how blockchain can provide a resilient, transparent, and secure framework for Industrial IoT applications, improving efficiency and trust across smart manufacturing and industrial automation environments.