Yes....there are different grades of SS screws, the cheap import ones have very little nickle in them so they will rust. The more nickle, the more rust resistance, the more nickle...the less attraction to a magnet !! Same for kitchen sinks, if a magnet grabs the sink, it will rust...most cheap SS screws will attract a magnet, gotta get the good ones, but beware, real good quality SS screws can be soft and easier to break. While nickle makes steel not rust, it does not add toughness or strength. For boating purposes, high syrength bolts are not needed so real stainless steel can be used. When real SS screws are used, there is no need to worry about non similiar metal corrosion, but when cheap, low nickle SS is used you can get dissimiliar metal corrosion. Retired toolmaker here, worked with SS for more years than I can remember, carry a small magnet in your pocket whenever shopping for SS anything, don't listen to the salesman !!