DIY treating untreated lumber for deck usage?

I need to build two decks on my house under construction. I have a small pile of 2x10s left over among other lumber. Are there any good products out there I could use to treat these for use on a deck? One of the decks is fully tucked under a roof with walls. I’m sure I could find another use for the lumber if this isn’t feasible. Just hoping to clean up some space and make use of materials on hand.

 

Danke für die konkreten und sachlichen Hinweise, sie haben mir das Thema sehr verdeutlicht.

Tiefziehmaschine

 

I ended up using raw linseed oil cut with turpentine for a deck a few years back, reapplying every season. It worked okay, though it takes time to dry. I found some decent application brushes and traditional finishes at this shop that helped make the process smoother. Not a permanent solution, but it bought me some years before switching to better wood.