How often should a ceramic-coated car be decontaminated?

There is no universal interval; the right frequency depends on how much contamination the car is exposed to. A car parked near rail lines, industrial sites, sprinklers or salted roads may need iron or mineral decontamination far more often than a garaged weekend car. Practical signs include reduced beading after a proper wash, a rough or grabby feel, visible orange specks or spotting that ordinary washing does not remove. Decontaminate when those signs appear rather than on a fixed calendar.