Anti-Slip Coefficient Engineering Data
Static vs. Dynamic Coefficient of Friction
Coefficient of friction (COF, or mu) is the ratio of friction force to the normal force pressing two surfaces together. Static COF describes the force to start a shoe sliding; dynamic COF describes the force to keep it sliding. In practice the static value governs slip - the moment a foot starts to move is where falls happen. Different test apparatuses measure different footwear and surface conditions, so a COF number is meaningless without the test method and the contamination state.
ASTM and ISO Slip-Resistance Test Methods
| Standard | Apparatus / Principle | Measures |
|---|---|---|
| ASTM D2047 | James Machine (horizontal pull of a standard shoe sole) | Static COF of polished/walked surfaces; common for floor polish |
| ASTM D1677 | Inclined plane (articulated leg on a tilting board) | Static COF under wet and dry conditions for safety surfaces |
| ASTM F1677 | Mark II / English XL (articulated foot, portable) | Field-use static COF on installed surfaces; widely cited by safety officers |
| ASTM F2913 | BOT-3000 (floor friction tester) | Dynamic COF; modern lab and portable reference for walkway safety |
| ISO 13287 | Human-footwalk method with a specified boot | Slip resistance of safety footwear on contaminated surfaces (ISO 20345 family) |
A ZeAllgrate COA or test report states the standard, the contaminant (dry, wet, oily) and the footwear/shoe material - compare like with like only.
COF by Surface and Contamination (Indicative)
| Surface | Dry COF | Wet COF | Oily COF |
|---|---|---|---|
| Grit-top (silica / carbide) | 0.8 - 1.0 | 0.6 - 0.8 | 0.4 - 0.5 |
| Concave (dished meniscus) | 0.6 - 0.7 | 0.5 - 0.6 | 0.3 - 0.4 |
| Convex (raised crown) | 0.6 - 0.7 | 0.5 - 0.6 | 0.3 - 0.4 |
| Smooth (cleanable) | 0.5 - 0.6 | 0.3 - 0.4 | 0.2 - 0.3 |
| Covered grit-top (integral cover) | 0.8 - 1.0 | 0.6 - 0.8 | 0.4 - 0.5 |
Indicative ranges from ZeAllgrate in-house testing against ASTM F1677-style articulation; actual values depend on grit grade, shoe material and contamination. The wet and oily columns are the design drivers.
What the Codes Expect
| Reference | Threshold | Applies To |
|---|---|---|
| OSHA (29 CFR 1910 walkways) | Static COF at least 0.5 recommended | General industry walking-working surfaces |
| ADA / accessible routes | COF at least 0.6 on accessible walking surfaces | Public accessible routes in the USA |
| UK HSE / BS | Wet ramp / pendulum value at least 0.36 | UK industrial and public wet environments |
| ISO 13287 / footwear | Per safety footwear standard on wet contaminated surfaces | Europe / footwear-and-surface pairing |
Design to the wet value, not the dry one. A grit-top surface holds its wet COF above the OSHA and HSE thresholds; a smooth surface drops below them as soon as it is wet.
Grit Material, Grade and Wear Life
| Grit Type | Hardness | Best Used For |
|---|---|---|
| Silicon carbide | Very hard (Mohs 9+) | Maximum wet/oily traction; the premium grit for offshore and wash-down |
| Aluminum oxide | Hard (Mohs 9) | Good general grit, slightly cheaper; fine for industrial walkways |
| Silica / natural grit | Medium | Economical standard grit-top; adequate for moderate wet service |
Grit Grade
Coarse grit (16-24 mesh) gives the highest wet traction but a rougher feel; finer grit (30-46) is more comfortable underfoot and still meets wet thresholds. Specify by environment, not by feel.
Wear Life
In heavy foot traffic a bonded grit-top lasts 5-10 years before the grit wears flush. Wheel traffic (forklifts) abrades grit faster; re-coat or replace when wet COF drops below the design threshold.
Contamination Effects and COF Maintenance
| Contaminant | Effect on COF | Design Response |
|---|---|---|
| Water / wash-down | Thin film reduces all surfaces; grit-top retains most | Specify grit-top; keep drainage open |
| Oil / grease | Severe reduction; smooth surfaces become hazardous | Grit-top with regular degreasing; avoid smooth in oily zones |
| Process chemicals | Depends on chemistry; check resin compatibility | Match resin (ZeAll VE for strong chemicals) and grit-top |
| Ice / frost | Near-zero COF on any surface | No surface solves ice; provide drainage and de-icing management |
| Dust / powder | Can build a slippery layer on textured surfaces | Smooth for dust-trap risk; clean regularly |
Cleaning Schedule
Pressure-wash grit-top quarterly in wash-down service; more often in oily areas. A clean grit surface keeps its COF; a clogged one behaves like smooth.
Grit Re-Coating
When grit wears flush, a fresh bonded grit coating restores the wet COF without replacing the panel - check with ZeAllgrate for the correct resin-compatible grit system.
Choose the Surface by Environment
| Environment | Recommended Surface | Why |
|---|---|---|
| Permanent wet / wash-down / food | Grit-top | Holds wet COF above OSHA 0.5 and HSE 0.36 |
| Marine / offshore / chlorides | Grit-top, SS316 clips | Wet salt service plus corrosion-resistant hardware |
| General industrial dry | Concave / convex | Good dry traction, lower cost than grit |
| Oily / chemical process | Grit-top, vinyl ester resin | Wet/oily traction plus chemical resistance |
| Cleanroom / food contact / barefoot | Smooth | Cleanability beats traction where contamination is controlled |
Need a COF Test Report for Your Environment?
Tell us the contamination and footwear standard - ZeAllgrate supplies COF data by ASTM F1677 / F2913.
Source: ZeAllgrate (Fiberglass Grating Manufacturers Council / ACMA) design guidelines; ASTM International; ISO 14122; OSHA 29 CFR 1910. Indicative data for specification guidance only — final design verified by ZeAllgrate engineering against certified load/span charts.