Comparing chemical and plasma modification of stainless steel surfaces – Relevance for adsorption of adhesion promotor vinyltrimethoxysilane (VTMS)

Coated stainless steel surfaces with silane compound coupling agent are implemented in many industrial applications. For vinyltrimethoxysilane (VTMS) adsorption optimization, surface modification of stainless steel type V2A was performed with plasma, ozone and in sodium hydroxide (NaOH) solutions. Subsequent a systematic study of a central composite design of experiments (DoE) accomplished with X–ray photoelectron spectroscopy (XPS) data. Similar results in ozone, oxygen (O2)–, and water (H2O)–plasma treatment led to a detailed presentation of the results from the O2–plasma and NaOH treatment. Treatment effects on the surface roughness were determined using atomic force microscopy (AFM) and the functional groups of VTMS on the surface with surface enhanced Raman spectroscopy (SERS). All treatments resulted to a reduction of C and a higher oxidized surface whereas the Fe/Cr–ratio and OH-content were changing significantly after NaOH treatment. Only the root mean squared (RMS)–values calculated from the AFM images of NaOH treated V2A samples indicated an increased coverage of VTMS after longer treatment time in higher concentrated NaOH solutions. The results of this study enable setting the amount of VTMS bonding to the surface of V2A due to NaOH pretreatment.