I have to agree with Duncodin. If the salt got there when you drove in salty conditions, it'll get washed out if you drive in wet conditions when the salt on the roads has been washed away by rain. The last time I drove my Z was home from its MoT test at the end of November last. It was frosty and the gritters had been out so I dove straight into the garage, which is semi integral and therefor drier and warmer than most, and there it has lain ever since. I rarely use it in winter except for a New Year's Day run to the south coast for lunch at Beachy Head. Ill health in my family has put paid to Z use since last year so it didn't even get that day out. next time there's been a few inches of rain and no gritting, I'll take it out for a fast run to soak the underside. No comments were made about rust except suspected corrosion on the rear brake pipes - "...covered in grease or similar..." was the comment.