Keawhan, C., P. Wongpanya, N. Witit-anun, and P. Songsiriritthigul. 2012. “Corrosion Behavior of AISI 4140 Steel Surface Coated by Physical Vapor Deposition”. Journal of Metals, Materials and Minerals 22 (1). Bangkok, Thailand. http://jmmm.material.chula.ac.th/index.php/jmmm/article/view/25.