Prestone Anti-Rust in F250 Ford Powerstoke 6.0 to prevent block rust Rotella ELC coolant backflush

I've had an issue with block rust once I converted my powerstoke 6.0 to Rotella ELC coolant. I wanted to control rusting and decided to give this Prestone anti rust a try. The problem is my oil cooler keeps getting clogged with rust.
Prestone Anti-Rust
https://www.amazon.com/gp/product/B07GQ5XC8M/ref=as_li_tl?ie=UTF8&tag=fintechcomm0f-20&camp=1789&creative=9325&linkCode=as2&creativeAS=B07GQ5XC8M&linkId=0df6170ce622f4b6f8a6d931dc72682c
Big Bottle
https://www.amazon.com/gp/product/B001DKNS2I/ref=as_li_tl?ie=UTF8&tag=fintechcomm0f-20&camp=1789&creative=9325&linkCode=as2&creativeAS=B001DKNS2I&linkId=042b01aa15ac654136958497bb21a91d