If you ride in the wet and do not undertake heroic measures (e.g., extremely meticulous post-ride wipe-downs), you will see rust on certain exposed parts, such as the inside surfaces of bolt heads. I recommend learning to live with it.

I regard full-coverage fenders, with large/long mudflaps, as the best protection against the ravages of road spray, with its delicious mix of toxic and caustic chemicals. A front fender with a low mudflap is especially valuable in protecting your bottom bracket, crankset, feet & pedals, and chain from spray. Perhaps others can advise you on how to fit full fenders on a Sirrus, if it's possible. A seatpost-mount rear fender -- IF it's mounted suitably close to the tire, as they commonly are not -- can protect the rider's rear end, but it's only partially effective in protecting the bike.

Watch for drivetrain rust, especially on the chain, which can shed its lube quickly in the rain. You might try a tenacious lube, such as Pedro's Syn Lube. Other lubricated contact points, such as brake pivots and the ends of shift and brake cables, will need attention too. I tend to be seriously aggressive about regularly cleaning and lubricating my bike during rainy and snowy periods, though others with a more laissez-faire attitude will probably report perfectly good results.