cast iron is widely used in manufacturing irrigation sluice gates penstocks.
Magnetism links up You take 2 magnets, both same direction they join forces even if they donot touch, but simply enter e achothers field. So yes magnetism can pass thru magnetic materials. Also, ANYTHING is magnetic given you push enough electricity thru it.
From pedia: Cast iron usually refers to grey cast iron, but identifies a large group of ferrous alloys, which solidify with a eutectic. Iron accounts for more than 95%, while the main alloying elements are carbon and silicon. The amount of carbon in cast irons is the range 2.1 - 4%, as ferrous alloys with less are denoted carbon steel by definition. Cast irons contain appreciable amounts of silicon, normally 1 - 3%, and consequently these alloys should be considered ternary Fe-C-Si alloys. So, in general: iron, carbon, and silicon, with the carbon content being higher than in steel, making the cast iron more brittle than steel.
