Thought i would post an update. Over four years and it mostly looks good. Interesting that the factory joint on the sides now looks the worst. I will probably just ruff it up and put another coat of paint. I wonder if ash is corrosive
Potash (/ˈpɒtæʃ/) includes various mined and manufactured salts that contain potassium in water-soluble form. The name derives from pot ash, which refers to plant ashes or wood ash soaked in water in a pot, which was the primary means of manufacturing the product before the Industrial Era. The word "potassium" is derived from "potash".
Potash (especially potassium carbonate) has been used in bleaching textiles, making glass, ceramic, and making soap, since about AD 500. Potash was principally obtained by leaching the ashes of land and sea plants.
I used a Wire Wheel on my 5" grinder to remove the Rust. There were some minor pinholes. I used fine stranded fibreglass filler to cover the entire seem. Sanded and painted with a Rust Paint. All good now.