The benefit of a guy rope fitted with a marquee trace spring is that you can use much larger pegs or stakes and are best suited to large shelters or situations where wide sand pegs are the preferred anchor.
The rope is 6mm polyethylene and all the fittings are zinc coated for corrosion protection whilst the Supa Peg Rope Runner offers set and forget stability.
With the trace allowing for stretch in the fabric, and the rope runner offering grip that doesn't need adjusting, these guy ropes, when combined with good ground anchors, make the ideal anchor system for shelters set up for long periods.
Marquee trace springs accommodate large pegs and stakes
These trace springs are made from zinc coated steel, so whilst they can rust, they'll do so at a much slower rate. You shouldn't have any issues with coastal camping, I'd just get into a good habit of rinsing with fresh water between trips to get the absolute longest life out of them. Hope that helps!