Schottky diodes failing

I have been using Schottky diodes of different current forward capacities because they are failing. The diodes connect underground pipelines and underground grounding systems to allow the DC due to train interference to go to the ground without affecting the pipeline. The Schottky diodes are good in this application because they have a low forward voltage. But I have tried diodes with 1, 3, and 5 amps forward current, which fail. I even put three of them in parallel, thinking that the problem could be the current, and still, at least one would fail, allowing the current in both directions. What are we doing wrong that makes the diodes fail? Are there any other diodes or robust Schottky diodes that we can use? The diodes are being installed underground in hand holes, but they are not touching the ground or the water directly. Thank you in advance, for your answer,

Rogelio de las Casas

Assuming a business is funding this project, Iā€™d install a transient signal logger on the diode and find out the exact frequencies and voltages present at the time it fails. With that data in hand it will be much easier trying to solve the problem(s).

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