We’ve used 17 cu ft steel dump carts for manure and wet bedding for years. They work fine but steel does not last forever with caustic urine and manure in it (we do rotate what goes in which cart each week). We’ve tried everything to eliminate or at least reduce rust and corrosion. We haven’t been able to find a similarly sized non-metal dump cart with a removable tailgate so we’re stuck with this steel issue. We’ve used everything from stuff used on boats, undercarriages of cars, etc. We’ve tried lining carts with stall mats. We rinse out and air dry between uses. These carts are not cheap and we’d sure like to get more than 2-3 years use out of them. Our manure/bedding gets dumped on the complete opposite side of our property so a cart is essential! Thanks for any ideas (or if you’ve run across a 17 cu ft non steel dump cart!)
How about this one?
Or this one
https://www.lowes.com/pd/Polar-18-cu-ft-Plastic-Dump-Cart/50328585?store=1569&cm_mmc=shp--c--prd--sol--ggl--PMAX_SOL_000_Priority_Items--50328585--local--0-_-0&gad_source=1&gclid=CjwKCAiA-Oi7BhA1EiwA2rIu2-i4_goebSxrgysdFdIoKkhMVrksPXH2V8J5xefE0DxKtPm3m3yr9BoCj7YQAvD_BwE&gclsrc=aw.ds
How about spray on or roll on bed liner?
Because of where we need to dump, we have to have a removable tailgate (or whatever you want to call it). These don’t. But thanks!
Tried that first thing! Works for awhile. Thanks,
That certainly will make it tougher to find - you need a blow-molded type. I wonder if a local fab shop would make you one out of stainless? Might be worth a call!
Flex seal might work, spray or paint-on. I’ve used the tape to create a seal in my trailer, and it works well. I haven’t used it for what you need so can’t comment other than to say it seems like a reasonable option. I asked ChatGPT the question and they assured me that yes, it will work to seal a wheelbarrow, so there’s that.
I’m wondering if you hosing it out every use is causing an issue, allowing the muck to penetrate deeper than it would as just pee-soaked shavings. Maybe try leaf blowing it out, instead of hosing? Is it stored in sun or in shade?
This is what we’re currently using. So far, it’s about the best!
We switched to hosing after a few years of NOT doing so in the hopes it might help. I’d say we’re hit or miss doing it. Stored outside the barn (hooked up to ATVs).
Have you ever tried Farm & Implement paint? It’s designed for rust protection and is weather resistant, and can probably put up with a fair amount of abuse.
Rust-oleum Farm and Implement Paint
Krylon Farm and Implement Paint
As with all paint jobs, site prep is key. 
