Apparently the answer is "it depends on the soil chemistry." DURABILITY OF REINFORCED EARTH STRUCTURES: THE RESULTS OF A LONG-TERM STUDY CONDUCTED ON GALVANIZE

Apparently the answer is "it depends on the soil chemistry." DURABILITY OF REINFORCED EARTH STRUCTURES: THE RESULTS OF A LONG-TERM STUDY CONDUCTED ON GALVANIZED STEEL. M DARBIN, JM JAILLOUX, J MONTUELLE, and ROMANOFF Proceedings of the Institution of Civil Engineers 1988 84:5, 1029-1057 https://www.icevirtuallibrary.com/doi/abs/10.1680/iicep.1988.508 https://www.icevirtuallibrary.com/doi/abs/10.1680/iicep.1988... (pay article) Others here https://scholar.google.com/scholar?q=galvanized+soil https://scholar.google.com/scholar?q=galvanized+soil The following appear to be true: (1) HDG (or equivalent) has an order of magnitude greater resistance to corrosion in soil than uncoated steel, (2) corrosion rates are highly influenced by presence (or lack) of chlorides, sulfate, and citric acid in the soil, as well as temperature. Given the above, the suitability of galvanized steel in soil, at standard steel diameters and coating thicknesses, is either suitable (for low aggressivity soils) or non-suitable (for high aggressivity soils) over an example span of 20 years. Tl;dr: test and characterize the soil it's going to be in.