Nedox
NEDOX® is a surface treatment method to be used on steel, stainless steel, cast iron, copper, brass and copper alloys. The process combines the properties of electroless nickel and coating with polymers resulting in a number of improved properties:
- High hardness
- High wear resistance
- High corrosion resistance
- Non galling properties
- Low cofficient of friction
- Non-stick properties
- Close dimensions
- Uniform coating
- No post machining
There are various coatings within the NEDOX® family, all featuring the combination of properties but each of them optimised to one, or some, of them:
- Nedox® SF-2 Highest hardness and wear resistance in combination with best corrosion resistence, low coefficient of friction and non-stick properties. Approved for use in contact with food and drugs.
- Nedox® 10K-3 Delivers superior corrosion resistance, low coefficient of friction, non-stick properties and release properties up to 450°C. Approved for use in contact with food and drugs. Nedox 10K-3 is PFAS free.
- Nedox® NH-1 Good corrosion resistance, hardness and wear resistance in combination with low coefficient of friction.
- Nedox® NH-3 High hardness and wear resistance in combination with low coefficient of friction.
- Nedox® U-4 Best non-stick properties, especially against rubber and urethane, and at heat welding of plastics. Approved for use in contact with food and drugs.
- Nedox® FM-5 Best dry lubrication, lowest cofficient of friction, by a combination of MoS2 / polymer together with high hardness and wear resistance. Nedox FM-5 is PFAS free.
Technical information about Nedox coating
Basic coating build-up for the NEDOX® coating is an electroless nickel coating process. The term “electroless process” is used to describe methods of plating by means of chemical reduction instead of using current as in electroplating. The reducing agent used is sodium hypophosphite which results in a content of 9-12% of phosphorus in the produced coatings. This gives the coating a number of interesting properties. By combining thes with different types of treatment with polymers NEDOX® coatings ends up with additional improved properties and positive synergistic effects.
Sliding properties
The combination of the electroless nickel coating, the polymers and other organic materials are synergistic and together they give the NEDOX® coatings their unique combination of durable dry lubrication and high wear resistance. NEDOX® coatings lowers stick-slip effects in unlubricated contacts (the difference between static and dynamic coefficient of frictions is wery small) and offer a guarantee for safe function in applications with intermittent movements. The wear index of NEDOX® SF-2 at dry sliding contact is:
– against steel 03 * 10-14 m 2/N
– against NEDOX® SF-2 03 * 10-15 m 2/N
Also in oil lubricated applications working at lower sliding speed the NEDOX® coatings reduces friction and wear.
| Pin on disc test | Lubricated** | Non-lubricated |
|---|---|---|
| Nedox® SF-2 // Nedox® SF-2 | 0,08 | 0,12 |
| Nedox® SF-2 // hardening steel | 0,05 | 0,15 |
| hardening steel/hardening steel* | 0,10 | 0,35 |
*Case hardening steel SS2511, ground surfaces. ** Oil for pneumatic tools, Nynäs LB31
Coefficient of friction between different material couples in pin-on-disc test. Sliding speed m/s, contact pressure 45 MPa.
Also characteristic of the NEDOX® coatings are their anti-galling properties at very short and high loadings. Comparative oil lubricated galling test where NEDOX® SF-2 has been compared with case hardened and carbonitrided steel has been performed. In the test, the load is put on very quickly and held at the surface pressure during 0,1-1,0 s. In tests where both or one surface have been coated with NEDOX® SF-2, any galling has been detected.
Non of them have shown any galling though the force has exceeded the yield strength of the substrate.
In the graph below the level at which galling appears at differend sliding speeds have been plotted for the different materials.
Results of galling test with materials with different types of surface treatment´s, pin Ø3,0mm against disc, lubricated with oil Nynäs LB31
Temperature range
NEDOX® SF-2, NH-1, NH-3 and U-4 do withstand continiuos use from -200 to+350ºC. At higher temperatures decompositions of the polymers will take please. NEDOX® FM-5 is designed to be used between -50 and +260ºC. At higher temperatures the endurance of the dry lubrication properties will decrease.
Corrosion resistance
NEDOX® coatings show very good corrosion resistance. The polymers are chemically fully inert in almost all environments and electroless nickel shows excellent corrosion resistance due to its passive surface.
In order to achieve best corrosion protection with as thin coating as possible of NEDOX® NH-1, which has no completely tight cover of polymer coating, it is important than the substrate has a smooth, clean and pore-free surface. Non-metallic inclusions in the surface of the substrate material, carbides, sulphides etc. emanating from alloying elements or impurities, as well as a porous or rough surface can breed pores in the coating resulting in less corrosion protection. Corrosion speed of the coating is though in general very low in most environment as shown in table beside.
The organic coating on NEDOX® SF-2 covers the nickelcoating better and is therefore not affected to the same debree by the above. Corrosion protection properties of NEDOX® U 4 is only decreased by a very high and sharp surface roughness and sharp edges which can penetrate the organic layer and by larger pores in the substrate from which process liquids can bleed out and damage the coating.
Required coating thickness varies of course with environment severity as well as above mentioned interference from base material.
In Salt Spray Test in accordance with ASTM B117 test panels of low alloyed steel with surface roughness Rz -4 µm coated with 40 µm NEDOX® SF-2 or U 4 stand more then 2000 h without showing any effect of corrosion. 40 um NEDOX® NH-1 or FM-5 stand 1200 h in the same test.
| Corrosive liquid | Corrosion speed (μm/year) |
|---|---|
| Acetic acid | 0,8 |
| Acetone | 0,08 |
| Aluminium sulphate, 27% | 5 |
| Ammonium hydroxide, 25% | 16 |
| Ammonium nitrate, 20% | 15 |
| Brine, 3,5% CO2-saturated | 5** |
| Brine, 3,5%, H2S-saturated | 0** |
| Calcium cloride, 42% | 0,2 |
| Citric acid, saturated | 7 |
| Copper cloride, 5% | 25 |
| Etylene glycol | 0,6 |
| Ferro cloride, 1% | 200 |
| Formic acid, 88% | 13 |
| Hydriochloric acid, 5% | 24 |
| Lactic acid, 85% | 1* |
| Nitric acid, 1% | 25 |
| Oxalic acid, 10% | 3 |
| Phosphoric acid, 85% | 3 |
| Sodium carbonate, saturated | 1 |
| Sodium hydroxide, 45% | 0 |
| Sodium hydroxide, 50% | 0,2** |
| Sodium sulfate, 10% | 0,8 |
| Sulfuric acid, 65% | 9 |
| Water, distilled, N2-saturated | 0*** |
| Water, distilled, 02-saturated | 0** |
| Seawater (3,5% salt) | 0** |
* Can produce dark discoloration, **at 95°C, ***at 100°C.
Corrosion speed on NEDOX®NH-1 in liquids at 20°C
Hardness
The electroless nickel coating is a supersaturated solid solution of phosphorous in nickel resulting in stresses in the lattice and increased hardness in the coating. Hardness at plated is -580 HV 0,05. By heat-treatment of the coating, nickel phosphide, Ni3P which is very hard, precipitates resulting in increased hardness and wear resistance.
NEDOX® coating´s hardness and wear resistance vs heat-treatment temperature. Maximum hardness possible to achieve is -1000HV 0,05. NEDOX® SF-2 and U 4 are heattreated to maximum hardness of the electroless nickel coating. In NEDOX® NH-1 the hardness is -580 HV 0,05 and in NEDOX® NH-3 -800 HV 0,05. -580 HV 0,05 and in NEDOX® NH-3 -800 HV 0,05.
Hardness at elevated temperatures in NEDOX® and hard chromium coatings. The hardness in the NEDOX® coatings is not reduced, as in hard chromium coatings, until the working temperature exceeds ~350ºC.
Wear resistance
The wear resistance against abrasive wear is for homogenous materials proportional to the hardness of the material. The wear resistance of not heat-treated NEDOX® coatings are equal to steel with low carbon content with the same hardness. Steel with higher carbon content and equal hardness has better wear resitance as they have a larger amount of hard carbides wich strongly contributes to an improved wear resistance. Equivalent to that the hard nickel phosphides that are precipitated in the NEDOX® coatings at heat treatment contributes more to improved wear resistance than to higher hardness in the coating. NEDOX®SF-2 has better resistance against dry abrasive wear than hardened steel and is combarable with hard chromium coating and Tuff Trided steel. The wear resistance of NEDOX® NH-3 is combarable with steel hardened to 62 HRC and NEDOX® NH-1`s is better than ordinary low alloyed steel. The best wear resistance is achieved on material with low surface roughness, Rz 4 µm.
Coating thickness and dimensional changes
In order to meet the demands regarding corrosion and wear resistance with the NEDOX® coatings in different applications the folowing coating thickness are recommended:
- mild exposure* 5 to 10 µm
- moderate exposure 10 to 25 µm
- severe exposure 25 to 50 µm
- very severe exposure more than 50 µm
In design of components to be NEDOX® coated it is important to consider the dimensional change due to the coating. All surfaces that are coated get a dimensional increase equal to the coating thickness. Diameter dimensions of threaded parts or splines get a dimensional change of:
This means that a screw with 60º top angle of the treads coated with 25 µm get an increase in diameter of 0,1 mm.
Facts:
| Phosphorus content, % | ~10,5 |
| Density (10,5%P), g/cm2 | 7,75 |
| Melting temperature, °C | 890 |
| Magnetic properties:: | |
| NEDOX® SF-2, U 4, Oe | 100-300 |
| NEDOXⓇ® NH-1 | Non-magnetic |
| Electrical resistance: | |
| NEDOX NH-1, µΩ, cm | 90 |
| Thermal conductivity: | |
| NEDOX® NH-1, W/m K | 4 |
| Coefficient of thermal expansion | |
| (22-100°C), µm/m*°C | 12 |
| E-modulus, GPa | 200 |
| Tensile strength, NEDOX® NH-1, MPa | 700 |
| Ductility, % elongation | |
| NEDOX Ⓡ NH-1 layer on steel | 1,0 |
| Internal stresses, NEDOXⓇ® NH-1, MPa | 0 |
| Coefficient of friction, unlubricated | |
| NEDOX® FM-5 against steel | ~0,10 |
| NEDOX® FM-5 against NEDOX® FM-5 | ~0,05 |
| NEDOX® SF-2 against steel | ~0,15 |
| NEDOX® SF-2 against NEDOX® SF-2 | ~0,12 |
| Hardness, HV0,05 | |
| NEDOX Ⓡ NH-1 | ~580 |
| NEDOX® NH-3 | ~800 |
| NEDOX® SF-2 | ~1000 |
| Adhesion, MPa | |
| on carbon steel | >300 |
| on stainless steel and other metals | >140 |
Examples of applications
NEDOX® opens new doors to your design work and gives you possibilities for more cost efficient constructions NEDOX® is used in a wide range of applications. Below a few examples.
- Food and pharmaceutical industry: Oven rack, roasting rack, ladle, scraper, knife, rollers, housings
- Machine industry: Bushings, guide, piston, bolt, brake bolt, drum, saw blade, nipple, locking parts
- Vehicles: Slotted disc, axle, gear wheel, locks, door stop, bearings
- Pumps: Spreader, impeller, pump shaft, lock, pump housing, pump screw, gear wheel, piston
- Plastics: Core, ejector, mold tool, stripper plate, welding mandrel
- Packaging: Channel, slide rail, heat sealing rail, welding tray, roller, roller, funnel
- Aircraft: Rotor housing, sleeve, impact pin, drawbar, puller housing, bolt
Goods, type and size
NEDOX® NH-1 and NH-3 are available as both rack and barrel plating. Other NEDOX® processes are only available as rack plating. Maximum good size is 1 * w * h: 1100 * 550 * 800mm.