The leaf support is concerning and I would strip it to see how bad it is there. Any undercoat that’s more of a rubbery membrane than just a paint is something to be concerned about since it can trap moisture and accelerate the rust issue. If you encapsulate it with anything, it should be something like POR-15. Fluid film is fine as well and long as you do it yearly.

The leaf spring appears to just have surface rust which is easily treatable. That leaf support needs to be stripped and descaled of loose rust.

 

Thanks for the reply. Would you strip it completely before applying POR-15? Or would that just be an extra layer to add on to what’s already on there?

 

could always do a VIN search or such to see where truck was registered maybe?

 

The undercoating the dealerships sprayed on as part of their recall is useless. I own a 2004 Double Cab as well and a few years after they applied the spray the frame had rusted so bad in spots the dealership failed it for the state inspection. Yours looks like what the dealership sprayed on mine. All they did was cover up any problem areas and it doesn't stop the rust. The spray they used doesn't dry solid like the POR-15 and it slowly washes off. I've been using the black fluid film yearly ever since they failed it for the inspection and it hasn't gotten any worse. I would clean it all off and see if its just surface rust or a bigger problem.