WA uses dirt instead of salt but unless you wash your car afterwards then it'll be good to go. Besides, Manufacturers test their cars very rigorous so unless your car is from the 1990s on back, then you might need to worry.
Cars even come with something like a 10 year rust protection or whatever right? But as long as you wash it, it will be ok. If you want a very thorough wash, take it to a automated wash so it can get under the car. But I know how people feel about those things. I've never had any issue's washing my cars in there once a month just so the underside can get cleansed.