Nickel Mesh Composition: Elements, Alloys and Mesh Geometry

What "Nickel Mesh" Actually Means in Industrial Buying

The phrase covers at least three different products, and the elemental answer depends on which one is on the table. The first is woven wire cloth made from commercially pure nickel wire in the UNS N02200 or UNS N02201 family, where nickel is 99.0 percent or more of the mass and every other element is a residual. The second is a nickel alloy cloth, most often a nickel-copper grade such as UNS N04400 or a nickel-chromium-iron grade used for heat resistance, where the alloying elements are deliberate and can reach 30 percent or more. The third, and the one that causes most disputes, is a composite: a steel core with a nickel coating, sold loosely as nickel mesh because the surface is nickel.

The distinction is not academic. A woven cloth at 99.0 percent nickel is chosen for alkali service, for electrical conductivity and for electrochemical electrodes. An alloy cloth is chosen where strength at temperature or resistance to a specific acid matters more than conductivity. A coated product behaves like nickel until the coating is breached, and then behaves like the substrate. Any specification that names only "nickel mesh" without a UNS number and a coating statement is incomplete, and the elemental analysis of the delivered lot may legitimately differ from what the buyer assumed.

This article sets out what the elements in pure nickel woven cloth are, what limits apply, how the alloy variants differ, and how mesh geometry interacts with the choice, because in practice the two are bought together and are quoted together.

Elemental Composition of Pure Nickel Woven Wire

Wire for pure nickel cloth is normally drawn from Nickel 200 or Nickel 201 rod, with the material specification commonly cited as ASTM B160 for rod and bar in the wrought form. The chemistry limits are identical to those of the sheet grades: a minimum of 99.0 percent nickel, with carbon, manganese, iron, sulphur, silicon and copper all capped at low residuals. The table gives the standard limits that a buyer can reasonably require, and the practical comment on each element.

Element	Limit in Nickel 200, UNS N02200	Limit in Nickel 201, UNS N02201	Why the limit exists
Ni	99.0 % minimum	99.0 % minimum	Carries conductivity, alkali resistance and ductility; everything else is residual
C	0.15 % maximum	0.02 % maximum	Carbon above the solubility limit segregates as graphite at grain boundaries in hot service
Mn	0.35 % maximum	0.35 % maximum	Deoxidation residual in melting; excess raises resistivity
Fe	0.40 % maximum	0.40 % maximum	Residual from scrap and from contact tooling; affects magnetic response and corrosion film
S	0.010 % maximum	0.010 % maximum	Sulphur forms a low-melting grain boundary phase and causes hot cracking during drawing
Si	0.35 % maximum	0.35 % maximum	Deoxidation residual; excess reduces ductility of fine wire
Cu	0.25 % maximum	0.25 % maximum	Residual that lowers conductivity and shifts electrochemical behaviour

Two of these lines carry real commercial weight. Carbon is the reason a low-carbon grade exists at all: a cloth woven from Nickel 200 and used continuously above roughly 315 degrees C will embrittle as graphite forms at the grain boundaries, whereas Nickel 201 at 0.02 percent carbon does not. Sulphur is the reason that nickel cloth fails in sulphur-bearing atmospheres even at moderate temperature; the same boundary phase that troubles wire drawing causes intergranular cracking in service. Neither problem shows up at room temperature, which is why a mesh can pass a visual inspection and still be the wrong grade for a hot duty.

The residual elements also matter for analytical users. Iron picked up from drawing dies or from steel handling equipment will show as a few hundred parts per million, and cobalt and chromium can survive from the melt. For filtration duties this is irrelevant; for a battery current collector or an electrochemical electrode where the surface chemistry is the function, a residual iron level in the hundreds of parts per million is worth stating in writing.

Alloy Variants and What Each Added Element Does

When a buyer moves away from pure nickel, the added elements are no longer residual but structural, and the cloth is a different material rather than a different purity of the same material. The most common alternative is the nickel-copper family, represented by UNS N04400, where nickel sits at roughly 63 to 70 percent and copper at roughly 28 to 34 percent, with iron and manganese held to a few percent. The copper addition buys resistance to seawater and to hydrofluoric acid, and costs roughly a third of the electrical conductivity. A cloth of this type is correctly described by its UNS number, not by a trade name, and an order that names a trade name without a UNS number leaves the composition open.

The second family is nickel-chromium-iron, where chromium at around 15 to 23 percent and iron at 5 to 20 percent build a protective chromium oxide scale that survives at 800 degrees C and above. These alloys are oxidation-resistant and much stronger hot than pure nickel, but their electrical conductivity is a fraction of the pure metal and they are not suitable where the mesh is an electrode carrying current into a caustic electrolyte. The third family, nickel-molybdenum and nickel-chromium-molybdenum alloys, exists for hydrochloric acid and chloride pitting service; those are specialised and should be bought against a specific UNS number and a mill certificate, never on a generic description.

A practical consequence for inspection is that the alloy families can be separated without a laboratory. Pure nickel and the nickel-copper grade are both strongly attracted to a magnet at room temperature, so a magnet tells the buyer that the item is one of those two or a coated steel, and tells nothing more. Density separates them: pure nickel sits at about 8.89 g per cubic centimetre, the nickel-copper grade at about 8.80, and a nickel-coated steel at about 7.85. Weighing a known length and width of cloth and dividing by the geometric volume is therefore a better field check than any magnet, and a positive identification still requires optical emission spectrometry or X-ray fluorescence on a clean wire.

Mesh Geometry: Aperture, Open Area and Areal Weight

Elements decide what the metal is; geometry decides what the cloth does. Three numbers describe a woven cloth completely: the mesh count, which is the number of wires per 25.4 mm in each direction, the wire diameter, and the resulting nominal aperture, meaning the clear opening between adjacent wires. Open area follows from those, and areal weight follows from wire diameter and mesh count together with density. The table gives consistent values for pure nickel at 8.89 g per cubic centimetre, calculated from the plain weave geometry, so that a buyer can check a supplier figure against first principles.

Mesh count per 25.4 mm	Wire diameter	Nominal aperture	Open area	Areal weight	Typical use
10	0.50 mm	2.04 mm	64 %	1.37 kg/m2	Coarse screening, catalyst baskets, electrode frames
20	0.35 mm	0.92 mm	53 %	1.35 kg/m2	Support layers under finer cloth, gas distribution
40	0.25 mm	0.385 mm	37 %	1.37 kg/m2	General filtration, electrolysis cathodes
60	0.19 mm	0.233 mm	30 %	1.19 kg/m2	Polymer and chemical filtration
80	0.12 mm	0.198 mm	39 %	0.63 kg/m2	Fine filtration, battery current collectors
100	0.10 mm	0.154 mm	37 %	0.55 kg/m2	Fine filtration, shielding laminates
200	0.05 mm	0.077 mm	37 %	0.28 kg/m2	High-definition filtration, diffusion layers
325	0.035 mm	0.043 mm	31 %	0.22 kg/m2	Very fine classification, laboratory screening

The relationship is worth stating plainly because it explains most specification arguments. Nominal aperture in millimetres equals 25.4 divided by the mesh count, minus the wire diameter. Open area in percent equals the aperture divided by the sum of aperture and wire diameter, all squared, times one hundred. Areal weight in kilograms per square metre equals 0.550 times the square of the wire diameter in millimetres times the mesh count, for a density of 8.89 g per cubic centimetre.

Reading the table by column rather than by row shows the design trade-off. Cloth in the 40 to 100 mesh band tends to sit near 37 percent open area with areal weight between 0.5 and 1.4 kg per square metre, because weavers adjust wire diameter to keep the cloth stable. Cloth at 60 mesh with 0.19 mm wire is deliberately dense and strong, at 30 percent open area, and is chosen where the cloth must resist pressure or abrasion rather than pass flow freely. A buyer who asks for higher open area at a fixed mesh count is asking for thinner wire, which means lower burst strength and shorter life in a vibrating screen.

Weaving, Edge Finish and Dimensional Tolerances

Pure nickel wire is soft and work-hardens readily, so cloth is normally woven in the annealed condition and supplied either annealed or as-woven. Plain weave, where each wire passes alternately over and under one wire, is standard for mesh counts up to roughly 100 per 25.4 mm and gives the most stable aperture. Twilled weave, where wires pass over two and under two, is used for fine cloth from roughly 200 mesh upward because it allows a larger wire diameter at a given aperture and therefore a stronger cloth. Twilled Dutch weave, with different wire diameters in warp and weft, produces a filter medium with high strength and very small absolute filtration ratings; it is not described by a single aperture figure and should be ordered against a filtration rating and a flow requirement rather than a mesh count.

Roll width and length tolerances matter more with nickel than with steel cloth because the material is expensive and offcuts are costly. Standard rolls run from 1 m to 1.5 m wide, and a width tolerance of plus or minus 10 mm on a slit roll is normal. Length is usually measured under a light tension, and a tolerance of plus 100 mm on a 30 m roll is realistic; a roll that is short by more than that is a genuine commercial loss on a 1 m wide nickel cloth.

Edge finish is a specification item in its own right. A woven edge, where the weft returns at the selvage, holds the cloth square and prevents unravelling but adds thickness at the border. A slit edge is thinner and dimensionally accurate but will unravel if the cloth is handled roughly, so a slit edge in nickel should be secured by welding, by a folded hem, or by edge dipping before the cloth is installed in a vibrating frame. For pleated filter elements, the edge treatment decides whether the pleat pack holds its shape after a few hundred cycles.

For generic industrial cloth, the reference specifications most often called up are ISO 9044 for technical requirements and testing of industrial woven wire cloth, and ISO 4783 for guidance on aperture and wire diameter combinations. ASTM E2016 covers industrial woven wire cloth in the North American system. Naming one of these in an order, together with the mesh count, wire diameter and alloy UNS number, removes most of the ambiguity that a description alone leaves open.

Service Limits: Corrosion, Temperature and Contamination

Pure nickel cloth is at its best in caustic service. It resists sodium hydroxide and potassium hydroxide across a wide concentration range, including the hot concentrated liquors that destroy stainless steel by caustic stress corrosion cracking, and it is one of the few metals that can be used in anhydrous caustic handling. It is also resistant to neutral and alkaline salt solutions, to most organic acids in the absence of air, and to dry halogen gases at moderate temperature. Those properties are the reason nickel mesh appears in chlor-alkali plants, in caustic evaporators, and as electrode substrates in alkaline electrolysis.

It is at its worst in oxidising acid. Nitric acid attacks nickel rapidly, and aerated sulphuric acid is not a service condition for the pure metal. Chloride pitting occurs when an oxidiser is present, so hypochlorite and ferric chloride environments are not appropriate. In these duties a nickel-chromium-molybdenum alloy or a nickel-copper grade is the correct choice, and the mesh geometry is secondary.

Temperature limits are governed by oxidation and by sulphur. In air, continuous service above roughly 600 degrees C produces heavy oxide scale and rapid loss of wire section on fine cloth; a 325 mesh cloth at 0.035 mm wire can lose a meaningful fraction of its diameter in a few hundred hours. In sulphur-bearing atmospheres the limit is far lower, because sulphur embrittles the grain boundaries; nickel cloth in a hydrogen sulphide stream at 300 degrees C will crack along the wires rather than thin uniformly. Reducing and vacuum atmospheres allow higher temperatures than air, but the mechanical load on the cloth then becomes the limiting factor.

Contamination is the third limit and the one least often discussed. Nickel is catalytic for several reactions, and a nickel mesh used as a catalyst support can be poisoned permanently by sulphur, by lead, or by halides. In high-purity filtration, a nickel cloth can shed iron-rich particles from drawing residues in the first hours of service, so a pre-cleaning cycle in warm dilute acid followed by deionised water rinsing is worth specifying for any cloth destined for semiconductor, pharmaceutical or battery applications.

Order Parameters and Certificate Verification

A complete order line for nickel mesh has nine parameters: alloy with UNS number, mesh count per 25.4 mm, wire diameter, weave type, roll width, roll length, edge finish, surface condition, and the test document required. Anything omitted becomes a supplier assumption. The two most commonly omitted are the UNS number and the surface condition, and they are also the two that generate the most disputes, because a coated steel product and a solid nickel product can both be described as nickel mesh in good faith.

The certificate of analysis should report nickel, carbon, iron, sulphur, silicon, copper and manganese, and it should be traceable to the heat number stamped on the roll tag. Carbon deserves particular attention: a cloth offered against a low-carbon requirement should show carbon at or below 0.02 percent, and a certificate that reports only "nickel 99.5 percent" does not answer the question. Where the cloth will be used at temperature or in a corrosive duty, the buyer should also ask for the wire tensile strength and elongation, since a cloth woven from heavily cold-drawn wire will be strong but brittle and will crack at the selvage during installation.

At goods-in, three checks catch most problems. First, weigh a measured square metre and compare with the calculated areal weight from wire diameter and mesh count; a large discrepancy means the wire diameter is not what was ordered. Second, measure the aperture on at least ten openings in each direction with a travelling microscope or a calibrated pin set, and compare the spread with the tolerance in ISO 9044. Third, bend a single wire from the edge through 180 degrees; solid annealed nickel wire will bend without cracking, whereas a coated steel wire will show the substrate at the bend and a brittle alloy wire will fracture. These three checks take twenty minutes and are far cheaper than discovering the substitution in a filtration campaign.

Packing and storage follow from the material. Nickel cloth is soft and scratches readily, and a scratch on a 0.05 mm wire is a reduction in section. Rolls should be wound on a core, wrapped in paper or film, and stored on end rather than laid flat under load. Cloth should never be stored in contact with steel, because a damp interface produces a galvanic stain that is difficult to remove and shows up as an iron contamination result in the first flush of service.

FAQ

Q: What percentage of nickel is in pure nickel mesh?
Woven cloth made from Nickel 200, UNS N02200, or Nickel 201, UNS N02201, carries a minimum of 99.0 percent nickel under ASTM B160 chemistry, with carbon, iron, sulphur, silicon, copper and manganese held to residual limits. Anything described as pure nickel below that figure should be treated as an alloy or a coated product until proven otherwise.

Q: Does a magnet prove that a mesh is pure nickel?
No. Nickel is ferromagnetic below its Curie temperature of about 354 degrees C, and nickel-coated steel is also ferromagnetic, so a magnet cannot distinguish the two. Density measurement and optical emission spectrometry on a clean wire are reliable; weighing a measured area is a good first screen.

Q: What is the difference between Nickel 200 and Nickel 201 mesh?
The nickel content is the same at 99.0 percent minimum. Nickel 201 limits carbon to 0.02 percent against 0.15 percent for Nickel 200, which prevents graphite forming at grain boundaries in hot service. Any cloth used continuously above roughly 315 degrees C should be the low-carbon grade.

Q: How is the aperture of a woven mesh calculated from the mesh count?
Nominal aperture in millimetres equals 25.4 divided by the mesh count per 25.4 mm, minus the wire diameter in millimetres. For example, 100 mesh with 0.10 mm wire gives an aperture of 0.154 mm and an open area of about 37 percent.

Q: Can nickel mesh be used in nitric acid or hypochlorite service?
No. Oxidising acids attack pure nickel rapidly, and chloride with an oxidiser present causes pitting. Nickel-chromium-molybdenum alloys or a nickel-copper grade are the correct materials for those duties, and the mesh specification should follow the alloy choice.

Q: Why does nickel mesh crack in sulphur-bearing gas at moderate temperature?
Sulphur forms a low-melting grain boundary phase in nickel, so the wires crack intergranularly instead of thinning uniformly. The failure can occur well below the oxidation limit, often around 300 degrees C, and it gives little visible warning before the cloth fails.

Q: What should a nickel mesh certificate of analysis report?
Nickel, carbon, iron, sulphur, silicon, copper and manganese as a minimum, traceable to the heat number on the roll tag. For hot or corrosive duty, add wire tensile strength and elongation, because a brittle high-strength wire will crack at the selvage during installation.