This book chapter explores the intricate relationship between adhesion and surface modification in coating materials, emphasising the pivotal role that surface treatments play in enhancing the performance and durability of coatings. The chapter delves into various surface modification techniques, including mechanical, chemical, and physical treatments, and their impact on adhesion properties. Through a comprehensive analysis of how surface roughness, energy, and chemical composition influence adhesion, the chapter provides insights into optimising coating processes for diverse industrial applications. The discussion also highlights recent advancements in nanotechnology and their contributions to improving adhesion through innovative surface modification strategies. This chapter serves as a valuable resource for researchers and engineers aiming to develop more robust and efficient coatings for various environments. Surface treatment encompasses mechanical, chemical, and physical procedures to prepare substrates for coating application. Mechanical treatments like abrasive blasting and grinding enhance surface roughness for improved mechanical interlocking. Chemical treatments such as acid etching and alkaline cleaning boost surface energy and cleanliness, while physical methods like plasma treatment, ion implantation, and laser surface treatment alter surface properties to enhance coating adhesion and performance. The chapter investigates how these processes heighten coating adhesion, prevent corrosion, and strengthen wear resistance. It also explores characterisation and evaluation methods like surface energy measurement, chemical analysis, topographical analysis, and adhesion testing to gauge treatment effectiveness. Real-world examples from the aerospace, automotive, and electronics sectors demonstrate the practical applications and advantages of surface passivation and treatment techniques. The chapter concludes by examining current obstacles and prospects, emphasising the necessity for eco-friendly and sustainable practices and technological advancements to meet the evolving demands of diverse industries. The comprehensive overview underscores the critical role of surface modification and treatment in ensuring optimal performance and longevity of coating materials.