Gabion Wire Mesh Corrosion: Coated Steel vs Polypropylene

How steel gabion wire corrodes

Iron in the wire, water and oxygen are enough to start the usual reaction. Soil water, groundwater or seawater makes it faster because the water conducts. A lower pH, more chloride, and a higher temperature generally make it faster still. The wire loses section. The tensile strength goes with the section.

The hard cases for gabion wire are the ones buyers already know: salt splash, acid sulphate soil, some industrial ground, and water that stays salty. A drained, neutral soil is milder. It is not a free pass. A nick in the coating is still a nick.

Three patterns matter on mesh. The zinc can be used up before the steel is attacked. A small holiday in the coating can pit through the wire. The gap between twisted wires, or under a torn PVC jacket, can hold water and corrode faster than the open wire. A coating system has to be read with those patterns, not as a label on the roll.

Galvanized gabion wire

Hot-dip zinc is the usual coating on gabion wire. It works as a barrier, and it is sacrificial: where the coating is scratched, nearby zinc still protects the steel for a while. The coating weight and the wire diameter should be on the quotation. Do not treat every galvanized gabion as the same product.

How long the zinc lasts depends on the soil or the water, not on a year copied from another job. This page does not state a service life in years, and it does not state a corrosion rate in micrometres. Ask for the coating mass and the exposure the designer assumed.

After the zinc is gone, the steel is bare. A 2.7 mm body wire, a common size on hexagonal gabion mesh, then loses diameter in the same way any bare steel does in that ground. The time is a site calculation. Do not put a replacement year into the specification from a general note.

Galfan and PVC coatings

Galfan is a zinc-aluminium coating, often about 95% zinc and 5% aluminium. The aluminium changes how the surface film behaves, and many specifications use Galfan where plain zinc is not trusted. It is still a coating on steel. It is not a different metal, and it is not a stated multiple of the life of plain zinc. Compare the coating mass and the test the project asks for.

PVC-coated gabion wire adds a polymer jacket, usually over zinc or Galfan. In principle the jacket keeps water off the steel. In practice the jacket is cut by stone, by a tight bend, or by UV over time. At the cut, the wire can corrode in a crevice under the jacket. PVC is useful where the mesh stays buried in stone and is not dragged across site debris. It is not automatically better than Galfan, and it is not the same product as a polypropylene mesh with no steel core.

Polypropylene composite mesh

Polypropylene composite gabion mesh is stretched polymer, not a coated wire. There is no steel to oxidise and no zinc layer to consume. Chloride and a low pH do not start the rust mechanism that removes a wire. That is the reason it is offered as a steel-wire alternative.

It is not inert to every chemical, and it is not free of ageing. UV, heat, abrasion, a cut rib and a bad joint still matter. Supplier data for the mesh on this site, under Q/SCKJ 008-2023, includes carbon black of at least 2%, mesh tensile strength of at least 30 kN/m and a rib tensile strength of at least 2200 N. Ask for the test method. Do not turn a laboratory hour figure into an outdoor life.

Creep under a constant pull is a polymer question. A gabion basket is mostly stone sitting in a cage, not a tie-back. The designer still checks the connections and any place where the mesh is asked to carry a sustained load. Do not describe the mesh as maintenance-free.

What to compare, without a year table

In a mild, drained soil the coating on steel wire may be acceptable. Write down the coating and the soil. Do not paste a 40-year or an 80-year figure from an article.

In acid sulphate soil, salt splash or contaminated ground, ask whether the coating is the thing that will decide replacement. Polypropylene composite mesh is a candidate because the rust mechanism is absent. It still has to pass the project's tests for strength, joint, UV and abrasion.

Underwater, the steel question is coating plus abrasion from moving sediment. The polymer question is abrasion, the joint and whatever UV the mesh sees above the waterline. Pick the mesh after those are named, not from a ranking on a web page.