Tips & Recommendations


What is corrosion?

The ISO 8044 standard defines corrosion as a physical-chemical interaction between a metal and its environment, leading to modifications of the properties of the metal and often to a functional deterioration of the metal itself, of its environment or of the technical system formed by the two factors…

Corrosion is an entirely natural process, and its cost is extremely high since the annual loss is estimated to be 2.5% of the GNP.

What is the corrosion mechanism?

Four elements have to be reunited for corrosion to be initiated:

  • an anode;
  • a cathode;
  • an electrolyte, generally water;
  • a transfer of electrons.

Corrosion sets in progressively, following several steps.

For more details: corrosion mechanism

How to prevent corrosion?

For corrosion to set in, an electrolyte (generally, water) must transfer electrons.

To prevent this phenomenon from occurring, the process needs to be interrupted by a barrier applied between steel and water. This can be achieved by different means:

  • paint;
  • hot galvanising;
  • thermally sprayed zinc (TSZ);
  • thermally sprayed zinc-aluminium (TSZA);
  • duplex system.
Which are the different corrosion classes

As per the ISO 12944-2:2017 standard

  • C1 – very low
    • Heated buildings with healthy atmosphere. E.g.: offices, shops, schools, hotels.
  • C2 – low 
    • Atmosphere with a low pollution level. E.g.: rural areas.
    • Non-heated buildings with possible occurrence of condensation. E.g.: depots, sports halls.
  • C3 – medium 
    • Urban and industrial atmospheres, moderate sulphur dioxide pollution. E.g.: coastal area with low salinity.
    • Production rooms with high humidity and some air pollution. E.g.: breweries, laundries, food-processing plants.
  • C4 – high 
    • Industrial areas and coastal areas with moderate salinity. E.g.: chemical plants, swimming pools.
  • C5 – very high 
    • Industrial areas and coastal areas with high humidity and aggressive atmosphere, coastal areas with high salinity.
    • Buildings or areas with almost permanent condensation and high pollution.
  • CX – extreme 
    • Offshore areas with high salinity and industrial areas with extreme humidity, aggressive atmosphere and sub-tropical and tropical atmospheres.
    • Industrial areas with extreme humidity and aggressive atmosphere.
  • Im1 – immersion in fresh water
    • Structures in rivers (dams), hydroelectric power stations.
  • Im2 – immersion in sea or brackish water without cathodic protection
    • Immersed structures without cathodic protection. E.g.: port zones with structures. E.g.: lock valves, landing stages.
  • Im3 – burial in soil
    • Cisterns buried in the ground, pipes and steel piles.
  • Im4 – immersion in sea or brackish water with cathodic protection
    • Structures immersed into water, with cathodic protection. E.g.:  offshore structures

Anti-corrosion protective systems containing zinc

Hot-dip galvanising

There are different galvanising processes which consist of dipping steel in a bath of molten zinc at +/- 455°C.

This process is not limited though to only depositing zinc over a surface. Indeed, a metallurgical diffusion reaction also takes place between zinc and iron, which metallurgically binds zinc to the base steel.

Several zinc-iron layers are formed whose zinc concentration increases as the distance to the coating surface shortens.

The specifications of this process are found in the EN ISO 1461 standard.

The different methods are:

  • continuous or Sendzimir: continuous or Sendzimir galvanising process consists of applying a zinc coating over the surface of a metal strip when this is dipped at high speed in a bath of molten zinc. The metal strips, with thickness between 0.25mm and 6.3mm, are transformed into finite products after galvanising. The layer of zinc thus obtained is 15 – 30µm thick. Zinc-aluminium (Zn/Al) alloys can also be used in this process;
  • discontinuous batch galvanising after manufacturing: process during which finished products are dipped for a rather short time in a bath of molten zinc. The thickness of the total layer is generally between 80 and 120µm. Standard for discontinuous hot-dip galvanising or batch galvanising: EN ISO 1461;
  • centrifuge galvanising: only small parts, like bolts, nuts, threaded rods, etc., can be centrifuge hot-galvanised. After having been pre-treated, these parts are galvanised by batches in baskets or drums and are centrifuged when taken out of the bath, to remove the excess of zinc. The zinc layer obtained this way is thinner than in the case of discontinuous hot-dip galvanising. The minimum layer thickness is specified in the EN ISO 1461 standard. Products with threaded rods are separately standardised in EN ISO 10684.
Electrolytic galvanising / Electroplating

Electrolytic galvanising or electroplating is a process for surface treatment using electrolysis. Electrolysis uses an electric current to drive chemical reactions.

The steel part to be treated, degreased and stripped beforehand, is dipped in a bath containing an aqueous solution of zinc salts which will play the role of electrolyte. I.e. it will let through the electric current due to ion motion. The steel part is connected as a cathode to the negative terminal of the generator, and the anode, connected to the positive terminal of the generator, is composed of zinc. Under the action of a continuous current, zinc dissolves and is deposited on the steel part.

The process of electrolytic galvanising or electroplating can be continuous (metal strip, wire, tube) or discontinuous, i.e. in batches (small parts like bolts, nuts, etc.). The discontinuous process takes place in hanging baths or in perforated rotating drums.

The thickness of coating obtained by continuous electroplating is 1-10µm per side, while a coating obtained by discontinuous electroplating varies between 5 and 25µm.

The anti-corrosion protection of a zinc coating can be improved by chromium passivation which gives it a transparent green yellow colour or a straw yellow to metal blue colour (ISO 5002 and NF EN 10152 standards).

The advantages are:

  • good adhesion;
  • regular coating thickness on the exterior side of parts;
  • can be electroplated: stainless steel, cast iron and even plastic.

The disadvantages are:

  • reduced cathodic protection due the small coating thickness;
  • limited anti-corrosion protection since the lifetime of a zinc coating is directly proportional to the thickness of its layer;
  • the inner walls of hollow parts are not or very little protected since the current does not reach inside a steel part and hence there is no zinc deposit in that place (Faraday cage);
  • limited to small parts.

This method consists of melting metal either in wire or powder form inside a flame spray gun or an electric arc gun, and then, using compressed air, spraying the molten metal over the steel, stripped beforehand with abrasive jets. The metallising process is standardised: ISO 2063 STANDARD. Zinc sprayed in this way instantaneously solidifies in contact with the steel surface and forms a zinc coating. Anti-corrosion protection is thus immediate.

Since metallising coating is slightly porous, it is recommended to apply a sealer. Moreover, the porous character of the metallised surface provides an ideal substrate for applying an additional paint layer, either for aesthetic reasons or for reinforced anti-corrosion performances. This is called a duplex system (metal coat + paint).

The coating thickness can vary between 50 to 200µm, which is ideal for long-term protection against corrosion. This flexibility also allows the applicator to adapt to all corrosion classes and to technical specifications. The process can be carried out in a workshop or on-site and is perfectly suitable for structures too large to be hot-galvanised.

Two systems are generally used for the wire:

  • Metallising with an electric arc gun: this process consists of introducing two zinc or zinc-aluminium alloy wires into an electric arc spray gun. When these two wires come into contact, an electric arc forms and melts the zinc which is then sprayed using compressed air onto the surface to be metallised. Wires with finer diameter, generally 2.50mm max, are used for this type of spray gun.
  • Metallising with a flame spray gun: this process consists of introducing a zinc or zinc-aluminium alloy wire into a spray gun fed with a flammable gas mixture (propane or acetylene and oxygen). The wire across the gun is melted by combustion and then sprayed using compressed air onto the surface to be metallised. Wires with larger diameter, generally starting at 3mm, are used for this type of spray gun.

Process during which small parts are placed in a rotating drum containing zinc or zinc alloy powder and sand. This drum slowly revolves for more than three hours at a temperature of 380 to 400°C, and zinc binds with the metal base, by diffusion. Two zinc-iron layers (gamma and delta) are thus formed at the surface of the material, with coating thickness depending on the treatment temperature and length of time. The coating obtained is uniform, hard and resistant to abrasion and lasting corrosion. See EN 13811 standard for specifications.

The obtained thickness of the coating varies between 2 and 30µm.

Several post-treatments can be carried out: chromium passivation (grey finish), black oxide coating or lubricated finish.

Non-alloy carbon steels, HR steels, sintered material, iron and cast iron are very suitable for sherardising.

Fields of application: nuts and bolts, screws, building, railway, automotive.

Mechanical galvanising

Mechanical galvanising is a cold galvanising process through which zinc is mechanically applied onto small metal parts.

The parts to be treated first undergo chemical treatment and then are rotated in a drum with zinc powder, glass beads, water and chemicals. Due to the drum rotation, glass beads spray zinc powder by their impact onto part surfaces. An almost uniform coating is thus obtained, with thickness between 3 and 85µm.

As for the finish treatment, parts can be chromium-plated or oiled.

Mechanical galvanising can be applied on parts with a maximum length of 20cm, and +/-500g, such as bolts, nuts, lock smithery parts (EN ISO 12683 standard).

A mixture of zinc-aluminium can also be deposited using this process.

Zinc rich paint

Paints with high concentration of zinc are paints which contain zinc powder and thus benefit from the anti-corrosion properties relating to zinc, namely cathodic protection and barrier against corrosion.

Paints with high concentration of zinc are organic or inorganic, depending on what binder is used. They can be applied by brush or can be sprayed, but they must be applied onto a properly prepared steel surface.

Sacrificial anodes

A sacrificial anode is a zinc part used to protect another metal element from corrosion, by being oxidised in its place.

Sacrificial zinc anodes, attached to ship hulls, oxidise instead of steel and protect ship hulls as long as they are not completely oxidised.

Une anode sacrificielle est une pièce métallique en zinc qui permet de protéger un autre élément métallique de la corrosion en s’oxydant à sa place.

Contrary to other anti-corrosion systems containing zinc and forming a barrier between steel and electrolyte/water, an anode changes the electrochemical potential. The cathode becomes an anode.

Anti-corrosion performance of different systems

More details on the performance of different anti-corrosion systems which contain zinc, can be found in the EN ISO 14713-1:2009 standard.

Performance varies depending on the systems used, coating thickness and corrosion class.

For flame metallising with sealer layer, the following performances are expected:

For a 100 µm thickness:

  • class C3 (VL): 48-143 years,
  • class C4 (VL): 24-48 years,
  • class C5 (L): 12-24 years,
  • class CX (S): 4-12 years,

For a 200 µm thickness:

  • class C3 (VL): 95-286 years,
  • class C4 (VL): 48-95 years,
  • class C5 (L): 24-48 years,
  • class CX (S): 8-24 years.

Classification of the different metallising processes

History of metallising
  • At the beginning of the 20th century, Max Ulrich Schoop carried out tests in Zurich, spraying lead and zinc in order to produce a protective coating.
  • In 1909, Schoop obtained a patent for flame spraying using gas and oxygen combustion for melting the wire to be sprayed onto a substrate.
  • Schoop’s second patent dates back to 1911. This was a patent for electric arc metallising.
  • Thus, metallising technology was established.
  • At the beginning, metallising was used only for protection against corrosion.
  • The use of materials such as ceramics, plastic, oxides and many others started only after the Second World War.
Classification of the different metallising processes

The different metallising processes are classified according to the combustion energy used.

The following standard describes the different systems: DIN EN ISO 14917:2017.

A summary of all these processes:

  • metallising by electrical discharge or gas:
    • arc spraying (AS),
    • plasma (APS, VPS, APSS),
  • metallising using expansion of compressed gas without combustion:
    • cold gas spraying (CGS),
  • gas or liquid combustion metallising:
    • wire flame spraying (WFS),
    • powder flame spraying (PFS),
    • detonation gas spraying (DGS),
    • HVOF/HVAF powder spraying,
  • laser cladding (LC).
Metallising by electrical discharge or gas

Arc spraying (AS)

This process consists of introducing two electrically conductive wires as like zinc or zinc-aluminium alloy into an electric arc spray gun. When these two wires come into contact, an electric arc forms which melts the wire. The melted wire is then sprayed using compressed air onto the surface to be metallised. Wires with finer diameter, generally 2.50mm max, are used for this type of spray gun.

Materials used:

  • Electricity conducting wires.

Fields of application:

  • steel structures as anti-corrosion protection: bridges, wind turbines, etc.;
  • power plants as anti-corrosion protection or protection against wear;
  • machine manufacture as protection against wear and repair of machine elements.

For more details: method and equipment

Plasma (APS, VPS, APSS)

A plasma torch is an apparatus where a gas is forced through a choked electric arc. This electric arc is established between an anode and a cathode which are cooled by water circulation. The cylindrical anode is pierced at its centre for receiving the cathode and letting the gas flow through. The gas injected this way around the cathode will flow across the electric arc where it is ionised and then sprayed as a plasma. This plasma has ultra-high temperature (up to 20,000 K) and ultra-high speed. The coating material introduced into this plasma will be sprayed at ultra-high speed onto the substrate.

Materials used in powder form:

  • pure metals;
  • alloys;
  • ceramic oxides;
  • materials containing nickel;
  • materials containing cobalt.

Fields of application:

  • aviation: turbine blades;
  • waste incineration plants: high-temperature piping;
  • medicine: implants;
  • machine manufacturing: pistons.

For more details: method and equipment

Metallising using expansion of compressed gas without combustion

Cold gas spraying (CGS)

The basic principle of the cold spraying process is accelerating a gas to supersonic speeds in a nozzle. Powder is introduced in the high-pressure part of the nozzle and is sprayed in a “non-molten” state (gas temperature: 600°C) onto the substrate.

Spraying non-molten particles will remove or minimise negative effects encountered with other systems: high-temperature oxidation, evaporation, fewer oxides in the metallising layer.

Laboratory tests showed that the coating produced using this system is extremely dense and has outstanding adhesion.

Materials used in powder form:

  • copper;
  • zinc;
  • aluminium.

Fields of application:

  • automotive;
  • protection against corrosion;
  • electronics.

For more details: method and equipment

Gas or liquid combustion metallising

Wire flame spraying (WFS)

This process consists of introducing a zinc or zinc-aluminium wire into a spray gun fed with gas (propane or acetylene and oxygen). The wire across the gun is melted by gas combustion. It is then sprayed using compressed air onto the surface to be metallised.

Wires with larger diameter, generally starting at 3mm, are used for this type of spray gun.

Materials used:

  • wires;
  • bars;
  • cords.

Fields of application:

  • steel structures for anti-corrosion protection;
  • gearbox fork;
  • synchro ring;
  • piston ring.

For more details: method and equipment

Powder flame spraying (PFS)

Powder flame spraying is a simple process of thermal spraying which uses the energy of a chemical reaction. A powder material is introduced at the centre of an oxy-fuel flame produced by a blowtorch. The powder is then sprayed at high speed due to kinetic energy transferred by combustion gases. With over 100 different materials, the range of coats to apply is thus very wide.

Materials used in powder form:

  • metals;
  • plastics.

Fields of application:

  • rolling rolls;
  • bearing rings;
  • rotors;
  • extrusion screws;
  • steel structures for anti-corrosion protection.

For more details: method and equipment

Detonation gas spraying (DGS)

A detonation gun consists of a 25mm tube, one meter long, with a combustion chamber at its end. Powder is introduced at the same time as the combustion gas mixture (acetylene-oxygen) which detonates due to a spark. The shock wave thus created accelerates particle spraying. Particles going through a flame are thus molten and ejected at very high speed. This is a discontinuous system.

Materials used in powder form:

  • pure metals;
  • alloys;
  • ceramic oxides;
  • materials containing nickel;
  • materials containing cobalt.

Fields of application:

  • pump pistons;
  • turbine rotors in steam turbines;
  • medical engineering: implants;
  • oil and gas industry: gas compressors;
  • paper industry: calender rolls.

For more details: method and equipment

HVOF/HVAF powder spraying

A mixture of fuel-oxygen is continuously burned in a combustion chamber. Hydrogen, propylene, propane, methane and kerosene are used as fuels. Gas combustion will generate a high-pressure combustion reaction. The powder to be sprayed is introduced into the flame where it becomes molten and is then strongly accelerated. This process is thus used for producing high-density coatings with optimum adhesion.

Materials used in powder form:

  • pure metals;
  • alloys;
  • carbides;
  • ceramics;
  • materials containing cobalt;
  • materials containing nickel.

Fields of application:

  • aviation: aircraft engines, landing gears, landing flaps;
  • gas and oil industry: valves;
  • building machinery: pistons, hydraulic cylinders;
  • power plants: turbines.

For more details: method and equipment

Laser cladding

Laser cladding (LC)

Laser cladding is a process used for applying an ultra-dense coating, metallurgically bound and almost perfectly pure.

The process is used for improving resistance to wear, to corrosion and to impact.

The process uses a high power laser accurately directed so as to create a welding bath where a metal powder is applied. The powder is brought by a protective inert gas and blown along the same axis as the laser beam. The specific nature of the laser is used to produce very dense coats, with a minimum of losses (< 5%) and yet with very good metallurgical adhesion.

Materials used:

  • Cobalt6;
  • NiCrMo;
  • FeCrB.

Fields of application:

  • high-temperature rolling blocks, resistance to corrosion and hardness, valves (Cobalt 6);
  • valve balls/seats, rolling blocks, parts for boilers used in waste incineration, oil refineries (NiCrMo);
  • coal and mineral pulverisers/wear plates/valves (WC/Ni);
  • valve balls/seats, boiler components, parts for boilers used in waste incineration, hydraulic bars, stabilisers (FeCrB).

Thermal spray with zinc and zinc-aluminium

Why use zinc?

Zinc will protect in more than one way:

  • like paint and galvanising, zinc will form a barrier layer;
  • zinc will then oxidise and form a patina layer providing additional protection;
  • zinc and zinc-aluminium have an additional advantage: zinc will provide cathodic protection, which means that in case of coating damage down to the steel, zinc will be sacrificed and thus prevent the steel from corroding.

For more details: zinc protection

Why use zinc-aluminium?

Zinc-aluminium metallising coating combines the advantages of the two metals.

Zinc-aluminium maintains its cathodic protection which is specific to zinc, and with the addition of aluminium, it provides high chemical resistance against aggressive environments.

Advantages of metallising using zinc-aluminium rather than pure zinc:

  • longer anti-corrosion protection than with pure zinc (salt spray test as per the ISO 9227 standard, and SO2 test as per the ISO 6988 standard);
  • more economical:
    • for the same surface to be treated and the same coat thickness, about 30% less wire is required. This is due to the much smaller volume of metallising residues,
    • higher covering rate, and thus a less expensive labour cost per m²,
    • total cost for metallising 1 m² certainly lower than when using pure zinc,
  • easier to use for the coating operator: since the metallising residue volume is smaller, there are fewer dusts in the spray booth.

For more details: zinc-aluminium protection


Sealing and duplex system

In order to increase resistance to corrosion, zinc or zinc-aluminium metal coats are often followed by a sealer layer or a paint system, the duplex system.

  • Paints containing acrylate, epoxy and polyurethane resin, are suitable. It is recommended to read the manufacturer’s specifications in order to assess suitability for every individual application.
  • Paints containing alkyd resins drying in the open are not recommended over zinc coats. They lead to the formation of blisters and peeling.
  • In the case of zinc and zinc-aluminium metal coats, the first sealer layer serves to close the pores as much as possible. In order to penetrate deep into the pores, paint has to be properly diluted. Due to this penetration, the sealer layer does not contribute to the total thickness of the duplex system.
  • In order to prevent a deposition of oxides or other contaminants into the pores of the metallised coat, the sealer layer has to be immediately applied after metallising, as soon as possible. The period depends on the atmospheric conditions, and in any case has to be applied before any condensation.
When should the first maintenance take place?

As per the ISO 9223 standard, the lifetime of a zinc coating before the first maintenance is *:

  • corrosion class C1:
    • for 100 µm of zinc: > 200 years,
    • for a duplex system: not applicable,
  • corrosion class C2:
    • for 100 µm of zinc: > 100 years,
    • for a duplex system: not applicable,
  • corrosion class C3:
    • for 100 µm of zinc: 50-100 years,
    • for a duplex system: not applicable,
  • corrosion class C4:
    • for 100 µm of zinc: 25-50 years,
    • for a duplex system: 45-90 years,
  • corrosion class C5:
    • for 100 µm of zinc: 13-26 years,
    • for a duplex system: 23-47 years,
  • corrosion class CX:
    • for 100 µm of zinc: 4-13 years,
    • for a duplex system: 7-23 years.

*Indicative time before the occurrence of 5% of rust.

Values are longer for zinc-aluminium.

Metallising parameters

Design of the parts to be metallised

Several points have to be considered.

Is metallising possible?

  • Easy, safe access.
  • Minimum metallising distance to be complied with.
  • Dead angles to be avoided.

For more details: accessibility

Will the design make corrosion easier/more difficult?

  • Presence of slots/openings between two elements.
  • Avoid places where water and dirt can stagnate.
  • Lifting aids to prevent coating from being damaged.

For more details: favourable/unfavourable design

Welds and edges?

  • Uninterrupted welds.
  • Round edges.
  • Grind the laser cut parts to create a certain roughness and remove burrs, if appropriate.

For more details: welds and edges

Surface preparation

Surface preparation has a considerable influence on the quality of a coating and especially on its adhesion. Several elements are thus to be considered:

  • degreasing: oil, grease, oxide and other dirt have to be removed;
  • blasting:
    • the surface to undergo blasting must be safely accessible,
    • blast the entire surface using compressed air, including weld beads, if any,
    • monitor atmospheric conditions during blasting,
    • after blasting, do not touch the surface with your bare hand,
    • metallising work has to be started as soon as possible after blasting,
  • degree of cleanliness: the degree of cleanliness to be reached as per the ISO 2063 standard is Ra 2.50 for zinc and zinc-aluminium, Ra 3 for aluminium;
  • degree of roughness: the surface roughness to be reached as per the ISO 2063 standard is Rz 50 µm to 100 µm.

For more details: surface preparation


Parameters of a metallising process

A certain number of parameters influence a metallising process:

  • current: it determines the wire advance speed. The melting rate depends on the current intensity;
  • voltage: voltage is an independent parameter which can be separately set. Voltage determines the thermal energy. The higher the voltage, the higher the flame temperature. Particles will hence be warmer, and thus have improved adhesion;
  • pressure of the gas atomisation: pressure has an influence on the coating structure. The higher the pressure, the smaller the sprayed particles and the finer the coating structure. Compressed air thus also has an influence on the porosity and the adhesion of the zinc coating, and on the roughness of paint layers;
  • metallising distance: depending upon the process (gas or electric arc), the ideal distance is between 80 and 180mm. Below 80mm, the coat may be too thick and thus lead to poor adhesion. On the other hand, above 180mm, the sprayed particles cool down before reaching the substrate, which increases the quantity of residues;
  • spraying angle: the optimum spraying angle is between 80 and 90°. These data are guaranteed only in automated spraying;
  • atmospheric conditions:
    • substrate temperature: 3°C above the dew point,
    • relative humidity: < 85%,
    • room temperature: > 5°C.

For more details: metallising parameters

Quality control

Quality control must be carried out before, during and after metallising.

  • visual inspection: the metal coat has to have a regular appearance, free of imperfections, without untreated surfaces, without non-sticking particles and without damage;
  • thickness inspection: coating has to achieve the thickness recommended in the technical specifications, without excessively exceeding it. Thus it is required to regularly inspect the thickness during and after metallising. Inspection can be carried out using magnetic induction equipment as per the ISO 2178 standard;
  • adhesion control: adhesion is an important factor which is directly linked to surface preparation. Control can be carried out on samples, using mobile or stationary equipment as per the ISO 4624 standard. The standard indicates a resistance to traction of 4MPa for a non-sealed zinc and zinc-aluminium coating;
  • microscopic analysis of a sample cross-section: since this is a destructive test, this examination is carried out on test plates.

For more details: quality control

Problems / Solutions

Poor coating adhesion

Possible causes for poor coating adhesion are, amongst others:

  • poor preparation of surface – cleanliness, roughness: follow the recommendations for surface preparation as per ISO 2063:2018;
  • too long metallising distance. The optimum distance for flame metallising is between 125 and 250mm, and between 80 and 180mm for electric arc metallising. If the distance is too long, particles are too cold when they reach the substrate;
  • spray gun installation: wrong voltage. Follow the manufacturer’s instructions;
  • wrong metallising angle: optimum angle between 70 and 90°;
  • damp surface to be coated: refer to the ISO 2063:2018 standard for the atmospheric conditions;
  • zinc coating achieves too low adhesion: change to ZnAl which achieves higher adhesion values.
Too rough metal coated surface

Possible causes:

  • too low gas pressure: increase pressure;
  • too large wire diameter: reduce the diameter;
  • nozzles are not ideal: replace the nozzles.
Flame spray gun: the wire is stuck inside the gun

Possible causes:

  • spare parts: check that the right spare parts (diameter, alloy) are installed under the right conditions;
  • metallising parameters: check the metallising parameters, follow the manufacturer’s instructions;
  • inadequate clearance: clean the nozzle hole with a suitable tool;
  • the wire is dirty or damaged: replace the wire with a clean wire. Prevent the wire from getting dirty, use wire spools;
  • the wire surface is corroded: a corroded wire can cause problems, always check the storage conditions (temperature, humidity, etc.);
  • knots: it is preferable to use wire spools;
  • the wire is twisted or not properly wound: replace the wire.
Electric arc spray gun: the wire does not come out

Possible causes:

  • spare parts: check that the right spare parts (diameter, alloy) are installed under the right conditions;
  • metallising parameters: check the metallising parameters, follow the manufacturer’s instructions;
  • check the guides and the sheaths: the wire should easily come out, clean if need be;
  • check if the wire comes out easily from the barrel or from the spools;
  • check the thumbwheel on the wire;
  • check the contact nozzles;
  • the wire surface is corroded: a corroded wire can cause problems, always check the storage conditions (temperature, humidity, etc.);
  • the wire is dirty or damaged: replace the wire with a clean wire. Prevent the wire from getting dirty, use wire spools;
  • knots: it is preferable to use wire spools;
  • the wire is twisted or not properly wound: replace the wire.

Safety measures

Personal protection

The personal protection equipment of a coating operator includes:

  • a hood or a helmet:
    • aimed at protecting the coating operator against particle spatters and exposure to dusts, while enabling him to breathe normally,
    • when using an electric arc spray gun, the glass on the hood has to be tinted for protecting the eyes from the harmful effects of the electric arc,
    • the hood has to be supplied with good quality breathable air,
    • zinc fumes have an unpleasant odour and can cause zinc fever. This fever occurs a certain time after metallising and generally goes away rather quickly. If this is not the case, a doctor has to be contacted,
  • an overall suit: it has to protect the front and prevent dusts from penetrating inside,
  • gloves: preferably made of leather which is non-flammable. They have to be thermally insulated and cover up to above the wrist,
  • safety shoes;
  • ear plugs: for attenuating the level of noise caused by the metallising work.
Flammability of metallising dusts

Zinc dust reacts with water to form hydrogen. This reaction is exothermic and temperature elevation can be enough, under certain conditions, to ignite zinc powder.

Precautions to be taken:

  • make sure not to let water penetrate inside the spraying booth, in order to prevent the combustion of zinc dust;
  • store metallising residues in closed, sheltered metal barrels;
  • avoid milling or grinding in the spraying booth in order to prevent spark formation;
  • welding work has to be carried out under argon.
Explosivity of metallising dusts

To our knowledge (over 40 years of experience in the field of metallising companies), no explosion ever occurred in zinc and zinc-aluminium spraying booths.

The risk of explosion depends on the size of the metallising dust. Every coating operator must thus test the explosive character of the dust they produce.

For information, a few data:

  • the values of the published general explosion parameters generally apply to relatively coarse powders;
  • auto-ignition temperature in a layer: 540°C and in a cloud: 690°C;
  • minimum auto-ignition energy (MIE): 640 to 960mJ;
  • minimum explosion concentration: 460g/m3;
  • maximum explosion pressure: 3.5 bars;
  • Maximum pressure for pressure increase: 120 bars/s;
  • flammability index: < 0.1. This 0.1 flammability index is considered to be low for such powders, but it strongly depends on the size of particles.
REACH declaration

Zinacor S.A. confirms that its products comply with the legal obligations as per Article 33 of the REACH regulation 1907/2006 (Registration, Evaluation, Authorisation and Restriction of Chemicals), which came into force on 01/06/2007.

Based on the present requirements with regard to information (as per Article 33), we can confirm that all Zinacor S.A. products mentioned below do not contain any of the substances from the ECHA “candidate list” (Substances of Very High Concern SVHC as per REACH article 59 in a concentration of more than 0.1% weight/weight)

  • Zinc anodes                                         Zinc strips
  • Zinc sheets                                          Zinc wire
  • Zinc-aluminium wire                            Tin-zinc wire
  • Zinc alloys for foundries                      Tin-copper wire
  • Zinc powder                                         Eco-Babbitt wire

Zinacor S.A. and its suppliers will check the present ECHA “candidate list” with regard to updates and continuous additions, and will provide the required information as per the REACH regulations. The currently valid “candidate list” is available on the website of the European Chemicals Agency via this link:

In Article 31 of the REACH Regulation, the requirements for Material Safety Data Sheets are regulated. According to these arrangements are Material Safety Data Sheets for substances and preparations, provided that they have hazardous properties.

Wires are no substances or preparations and have no hazardous properties. Within the meaning of REACH wires are articles. This means that no Material Safety Data Sheets required.

To give however information about our wires to customers, we have created the material information sheets. They are not in accordance with the regulations, but based on them (Structure, numbering ….).

With the transmission of material information sheets We have done more than the required obligation to provide information under Article 33 of the REACH Regulation.


Useful links


The Grillo group, the largest manufacturer of zinc products worldwide, and parent house of Zinacor.

The ‘International Zinc Association’ website which explains the general advantages of zinc.

The ‘Thermalsprayzinc’ website developed by IZA which explains in detail the advantages of zinc and zinc-aluminium coating.

The ‘Fédération des Métalliseurs de Belgique’.

The corrosion’ website which provides some general information on corrosion and protection against corrosion.

The ‘VOM’, Belgische vereniging voor oppervlaktetechnieken van materialen.

Download center

Security form - REACH - storage

Safety information Z850-851 Angleur GB

Safety information Z100-102 Angleur GB

Safety information Anodes Angleur GB

REACH declaration GB

Storage conditions GB

ISO Certificates

Certificate ISO 9001

Certificate ISO 14001

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