Properly sealed iron balusters on stairways or railings are very durable and protected from the elements. Iron is galvanized to protect it from oxidation. When painted, this effectively does the same thing. Because of their durability, major cleaning is hardly necessary. However, light, periodic preventative cleaning is beneficial.
Cleaning Iron Balusters
Interior iron balusters should be dusted along with other surfaces in the house. Wipe them down with a moist rag at least once a month. Make sure you get into the crevices. Other than that, there isn't much maintenance. After a number of years, outdoor iron balusters may need to be refinished, but all in all, they will last a long time.