Hey,
Iron sand shouldn’t have too much effect on the anodes themselves, (aluminium and iron are adjacent in the galvanic series*) however, the oil company would have probably put the anodes on top of concrete mattresses for added protection.
The iron sand will probably play havoc with the pipe tracker due to it’s magnetic properties. So, worth just keeping this in mind if using the pipe tracker.
On another note…iron sand has a tendency to heat up in direct sunlight, to such temperatures where it could cause minor burns.
*The distance on the galvanic series between two metals will also influence the likelihood of galvanic corrosion when the two metals are placed in conjunction with each other. For example, if aluminium is brought in contact with a steel pipe, the likelihood of corrosion is low since aluminium and steel are close together on the galvanic series. However, if a stainless steel fitting is used on an iron pipe, the likelihood of corrosion is much higher.
When galvanic corrosion occurs, the more active metals always become the anodes. This means that they are corroded, and in extreme cases can begin to leak. The less active metal becomes the cathode and is not damaged. Source: http://water.me.vccs.edu/courses/env110/lesson8_3.htm
Hope this helps…