Abstract-Silane molecular structure, including functionality and the length and character of organic modifying group, is the key factor that controls the performance of silane films in corrosion protection applications. In this paper, we review the use of neutron reflectivity to determine the influence of the bridging group on the swelling of bis-silane films. Our goal is to clarify the relationship between silane molecular structure, silane film morphology and water barrier performance while developing a database for optimizing the performance in anti-corrosion applications. In nitrobenzene, bis-trimethoxysilylpropylamine (bis-amino silane) swells more than bis-triethoxysilylethane (BTSE), a behavior that we attribute to differences in crosslink density. From swelling studies using deuterated nitrobenzene, we conclude that the crosslink density of BTSE is higher than that of bis-amino silane. High crosslink density leads to improved water-barrier performance and explains why bis-silanes are more effective than monosilanes as water barrier films. Bis-amino silane is found to swell more in water than in nitrobenzene, which indicates the importance of the character of the bridging group. The secondary amino group is the driving force for absorbing water. Finally, we observe exchange of the amine proton by the deuteron when bis-amino silane is swollen in heavy water.