Hardware fails quietly. At some crags it fails within a few years, with no visible warning before it breaks. This page sets out the mechanisms that reduce the lifespan of fixed hardware, and how VERTA addresses each of them.
The environment problem
The conventional explanation attributes the problem to sea air. The sampling contradicts it. Chloride is present in quantity at coastal crags where hardware remains intact for decades, and at coastal crags where it is destroyed in a few years, so chloride cannot be the decisive factor. Sulphate in the rock is what separates them.
How fixed hardware fails
Sulfide stress cracking (SSC)
Sulphate-reducing bacteria are anaerobic microorganisms. They metabolise sulphate instead of oxygen and give off hydrogen sulphide (H2S) as a byproduct. A bolt supplies the oxygen-starved pockets these bacteria need: the annular gap where glue meets metal, the contact zone between rock and steel, and the space beneath a hanger.
That hydrogen sulphide drives atomic hydrogen into the steel. It diffuses through the bulk metal over months and years, embrittling the steel from the inside, and the part fails by brittle fracture with the surface still looking clean. This is the mechanism the oil and gas industry designs against in sour service.
Grade does not help. The molybdenum in 316 resists pitting and general corrosion, not hydrogen entering the metal. Both 316 and 304 fail this way.
Titanium does not take up atomic hydrogen at rock-face temperatures and pressures, and its oxide film holds across the local acidity the bacteria create. ISO 15156-3 classes titanium as a corrosion-resistant alloy for H2S service. That is a materials standard for the oil and gas industry, not a certification of climbing hardware.
Stress corrosion cracking (SCC)
Chloride SCC is the explanation most often given, and it is a real mechanism in austenitic stainless. It requires a susceptible material, sustained tensile stress and a specific chemistry at the same time.
The chemistry is where it stops fitting. At ambient temperature the chloride concentration has to be extreme, and the low humidity that would concentrate it that far is incompatible with the 80 percent humidity beside the sea. Titanium Grade 2 is not susceptible either way.
Galvanic corrosion
Two dissimilar metals in contact, with an electrolyte present, form a cell, and the less noble one corrodes preferentially. A stainless hanger on a zinc-plated bolt corrodes faster at the junction than either metal alone. Pair titanium with a steel component and the steel is what goes. Single-metal systems remove the cell.
Crevice corrosion
Narrow gaps trap moisture and deplete oxygen. The trapped solution turns acidic and attacks the metal from inside the gap, where it cannot be inspected. Bolt holes, threads and overlapping components are the obvious cases.
Wire rope is the worst. Every contact point between strands is a crevice, water wicks along the lay and does not drain, and the inside of a swage cannot be inspected at all. The same anoxic geometry is what the bacteria colonise.
Titanium Grade 2 resists crevice attack in chlorides at ambient temperature. The documented susceptibility appears above roughly 70 °C, outside the service range of climbing hardware.
Weld zone corrosion
Welding alters the microstructure around the weld. Where shielding gas coverage is imperfect, chromium carbides form at grain boundaries and strip out the chromium that gives stainless its corrosion resistance. That is sensitisation, and it leaves a corrosion-prone band at the weld.
Materials compared
| Titanium Grade 2 | 316 | 304 | Zinc-plated steel | |
|---|---|---|---|---|
| Sulfide stress cracking | Resistant | Susceptible, grade does not help | Susceptible | Highly susceptible |
| Chloride SCC | Not susceptible | Susceptible | Susceptible | Rapid general corrosion once breached |
| Crevice corrosion | Resistant below 70 °C | Susceptible | Susceptible | Highly susceptible once breached |
| Galvanic risk to the component | Low | Moderate | Moderate | Anodic, corrodes first |
Zinc is a sacrificial coating, not a corrosion-resistant material. It is consumed in service and breached by installation, impact and abrasion. Once the base steel is exposed it has no corrosion resistance of its own.
Which crags this applies to
Coastal, tropical, limestone, and anchors failing faster than their age explains. The tell is brittle fracture with little visible corrosion, rather than hardware rusting where you can see it. Wall-wash sampling measures sulphate directly. Contiguous rock counts: if one sector destroys stainless, the rock either side of it is the same rock.
Materials we use
Titanium Grade 2 (TA2). Commercially pure titanium, used for all permanent outdoor hardware. Its corrosion resistance comes from a self-repairing oxide layer. Material is verified by third party optical emission spectrometry (OES) against ASTM B265 for every batch.
VERTA hardware is not certified to EN 959 or UIAA Standard 123. Certification is a planned step once the designs are frozen. What backs the hardware today is the material verification above and the published proof load and break test data.
Choosing titanium
Titanium costs more per anchor. It is worth that where going back to replace the anchor is expensive, difficult or unwelcome: sea cliffs, caves, tufas, multi-pitch, and any crag where a rebolt means another hole in the rock.
Titanium hardware · Safety and testing
References
- ISO, 2020. Petroleum and natural gas industries. Materials for use in H2S-containing environments in oil and gas production. Part 3: cracking-resistant CRAs and other alloys. ISO 15156-3:2020. Standard.
- Reeve, D., 2024. Thailand crags 1. Crag Chemistry. Web page.
- Reeve, D., 2025. SRB mediated bolt failure confirmed at Ourania. Crag Chemistry. Web page.
- UIAA, 2020. Update to UIAA Standard 123, climbing anchors. UIAA Safety Commission. PDF.