When trying to deposit materials on substrates such as SiO2, one commonly uses adhesion layers such as Ti or Cr. This is mainly due to the chemical reactivity of the two elements, allowing them to bond easily with the substrate.
After doing some reading into to the properties of Chromium, I learned that it is resistant to tarnishing, which I associate with reacting with the atmosphere. (One of the reasons why Cr is the key ingredients of Stainless Steel.) How is it that Cr is said to be chemically "reactive" alongside elements such as Al or Ti, if it doesn't tarnish easily?