This book provides a comprehensive and interdisciplinary exploration of advanced composite coatings and materials, emphasizing their design, synthesis, and performance in demanding environments. It addresses critical challenges in modern materials science, including corrosion resistance, antimicrobial functionality, and structural integrity under extreme conditions. The book begins with an in-depth analysis of microbiologically influenced corrosion (MIC) and introduces high-entropy alloys (HEAs) as a transformative solution for mitigating MIC in marine, industrial, and biomedical applications. Readers will gain insights into the mechanisms of microbial corrosion, electrochemical diagnostic techniques, and strategies for designing multifunctional materials that combine superior mechanical properties with antimicrobial performance. Key topics include thin-film deposition, crystal structure modeling using superspace symmetry, stress and strain analysis in nanostructured coatings, and the role of intrinsic stresses during ion irradiation. The text also explores cutting-edge approaches such as nitrogen doping, additive manufacturing of HEAs, and the integration of machine learning for predictive material design. Richly illustrated with diagrams, tables, and case studies, this textbook bridges theoretical foundations with practical applications, making it an essential resource for researchers, engineers, and graduate students in materials science, surface engineering, and corrosion technology.