The cable wire is a high grade stainless steel. It can discolor over time but if they use the right grade of stainless it will not rust. There are cleaning products available to bring it back to the original color I believe. There are several manufacturers of this cable wire and you could contact them about warranties

You can get plastic coated wire similar to the cable you would find on a sail boat.

Great question. As Peter McDonald Architect has mentioned, the stainless steel cable railing is marine grade stainless and will hold up to the salt and moisture in the air. A quick and easy cleaning will prove to be an effective practice in the lifespan of your cable infill and fittings. The Cable Connection is an American manufacture of Ultra-tec® cable railing infill. It is all made from marine grade stainless steel. For more information visit our site here: Ultra-tec®.

This is the cleaning product that we recommend. Read more about it here. It is available on our site's shopping cart here.

Wondering if the steel cable railing has held up? We are planning to build on the beach and worried about rust issues. Thank you

Any material on the beach is in a harsh environment but marine grade stainless is one of the best materials you can use. You should not have rust issues. Like noted above, periodic cleaning will help extend the lifespan and keep the stainless looking good. I would not have concerns.