The application sounds interesting. The use of Al/Zn as a thermal spray is used more and more on the Gulf Coast to extend the life of carbon steel under insulation for protection from the moisture and salt spray. I have not heard of its use for the interior of steel tanks, but the principle should still hold. You should gain extended life benefit from using an 85/15 aluminum/zinc metallizing on the steel interior -- especially for the water service. As I have no information for interior service, the caution would be what level of Al and Zn are added to the solutions, especially for the potable water service (check drinking water standards for allowable limits of Al and Zn). This is probably also true for fuel and non-potable water service, but to a lesser extent. The concerns for non-potable services are disposal limits (EPA), precipitation potential, and reaction during use.