Electropolishing is presently accepted like most efficient surface treatment obtaining high gradients in niobium RF cavities. This treatment seems to introduce more hydrogen in niobium than chemical etching [1]. We have investigated hydrogen contamination changes in various electrochemical conditions (like anodic protection) during chemical etching and electropolishing, and other conditions like hot water rinsing, hydrofluoric acid rinsing, etc... Hydrogen contamination near the surface is analyzed with HFS (hydrogen forward scattering). This technique allows exploring 200 to 300 nm of the surface (ie little bit more than the field penetration depth) and it is used to monitor the hydrogen up-take inside niobium in various electrochemical conditions.