The metal would only crack if there were already cracks in it
LOL, if thats the case, then no metal would ever crack! :P[/quote]
Sorry, did not explain that very clearly! All metal will have micro fissures and small cracks, but they will only be made worse by specific wear and tear. Only if the cracks are sufficiently large enough will ice get into them and expand to make the cracks worse. Generally metal is very durable and resistant to ice. I managed to sit through a couple of semesters of Material Science at Uni and managed to retain a small amount of knowledge!! In short it will not be an issue.