Can you order it without powder coating?
Wash it after each season, soak the mechanicals in anti corrosion wax. Seek out the damage and treat.
Just putting it out there but how hard is it to strip the hopper down?
I ask because if you really wanted it to last you could strip it, and send it off for blasting and galvanising?
Would cost but it’d see you out.
Failing that then as above - wash it and plenty of ACF50
Ok. That’s interesting. Any more info please?galv and fertilizer dont mix, as someone i know found out when they made hopper extensions