Passivating stainless steel is a preventative measure that draws the free irons away from the stainless steel or titanium part that could cause corrosion.
To be classified as "stainless," steel must have a chromium content exceeding 10.5 percent. The chromium helps the steel's iron portion resist combining with oxygen, which is how rust is generated. stainless Steel can rust but does so much less than other alloys.
This process will increase your parts' resistance to corrosion and provide a better, more aesthetically pleasing product for your customers. Since stainless steel is expensive, passivation is well worth the investment.