Hard Chrome Plating
We use hard chrome where a component surface requires greater wear resistance, lower friction or restoration of its working dimension.
What Does Hard Chrome Plating Include?
We tailor the scope of work to the condition of the component, the required surface and its function in the machine. We can apply the coating alone or carry out full component refurbishment.
Hard Chrome Plating of Surfaces
Application of a functional hard chrome layer to the working surfaces of industrial components and rolls.
Component Refurbishment
We remove the worn coating, inspect the component and restore the working surface.
Grinding and Polishing
After plating, the surface can be ground, polished or honed.
New Component or Reproduction
We manufacture new components from a technical drawing or reproduce the geometry based on a supplied sample.
Hard Chrome Plating Technical Data
We select the coating parameters according to the component function, substrate material and operating conditions. The values below define the typical range for hard chrome.
| Coating thickness | 10–200 µm as standard. Greater thicknesses are subject to individual assessment and quotation. |
|---|---|
| Hard Chrome Hardness | 850–1200 HVmeasured as Vickers microhardness. |
| Roughness after polishing | Ra 0.08–0.16 µmFor precision applications, a super-mirror finish of Ra < 0,08 µm. |
| Operating temperature | Full coating properties up to approximately 200°CContinuous operation up to approximately 400°C with a progressive decrease in hardness. |
| Substrate Materials | Carbon steels, stainless steels and cast iron. |
| Surfaces | External and internal surfaces. |
| Finishing | Grinding, polishing and honing, depending on the required working surface. |
| Maximum diameter | Up to 600 mm. |
| Maximum length | Up to 6000 mm. |
| Maximum weight | Up to 2500 kg. |
When Is Hard Chrome a Good Choice?
Coating selection is not determined by hardness alone. The wear mechanism, contact pressure, friction, possible impact loads and the condition of the component also matter.
Abrasive Wear
A hard chrome layer increases the working surface's resistance to abrasive wear.
Friction and Sliding Contact
Hard chrome has a low coefficient of friction, making it suitable for surfaces operating in sliding contact.
Contact Pressure and Mechanical Loads
Under point loads, impacts and bending stresses, hard chrome is a less brittle solution than ceramic coatings.
Refurbishment and Dimensional Restoration
A worn coating can be removed and reapplied, and hard chrome can also be used to restore the component's working surface.
Operating Conditions First, Coating Second
When selecting a coating, we analyse the wear mechanism, process medium, contact pressure, temperature, bending loads and refurbishment options. If the operating conditions point to another solution, we compare hard chrome with an appropriate coating technology.
A Good Coating Starts with the Substrate
The final result depends not only on hard chrome thickness and hardness. The component material, surface geometry and preparation before plating are equally important.
- Carbon steel - a standard substrate for hard chrome plating.
- Stainless steel — requires proper surface activation before electroplating.
- Cast iron — can serve as a substrate for a hard chrome coating.
- High-strength steels — require consideration of hydrogen embrittlement risk.
From Component Assessment to the Finished Surface
The scope of work depends on whether we are plating a new component or refurbishing a part already operating in the machine. We select the individual stages according to the substrate condition and the required working surface.
Defining the Requirements
We analyse the documentation, dimensions, component function and operating conditions of the working surface.
Component and Substrate Assessment
We inspect the surface condition, geometry and any features that may affect the subsequent scope of work.
Removal of the Old Hard Chrome
During refurbishment, the worn coating is removed electrochemically without eroding the steel core. This step is omitted for a new component.
Hard Chrome Plating
After substrate preparation, a functional hard chrome layer is applied in accordance with the agreed scope of work.
Grinding and Polishing
The surface then undergoes finishing: grinding, polishing and, for selected applications, honing.
Surface Measurement
Before shipment, surface roughness Ra and coating thickness are measured. A quality control report is supplied with the roll.
Refurbishment or a New Roll?
A worn coating does not automatically mean that a new roll is required. We make the decision after assessing the roll body, geometry and the component's ability to remain in service.
When Is It Worth Keeping the Existing Roll Body?
If the condition of the metal part and the wall thickness allow the required stiffness to be maintained, the worn roll can undergo another refurbishment cycle.
- removal of the worn hard chrome coating,
- inspection of the roll body geometry,
- restoration of the working surface,
- possible work on journals and bearing areas,
- replating with hard chrome and final finishing.
When Is a New Roll Required?
If the condition of the roll body does not allow the required geometry and stiffness to be maintained safely, the appropriate solution is to manufacture a new component.
- insufficient wall thickness,
- roll body condition that prevents further refurbishment,
- need to manufacture a new geometry,
- manufacture according to technical documentation,,
- possibility of reproducing the component from a supplied sample.
Technical Data Before Shipment and Quotation
We inspect the parameters of the finished surface and, before starting the job, assess the component condition and the required scope of work.
What Do We Check Before Shipment?
The finished surface is inspected for the parameters relevant to the applied coating.
- Ra roughness measurement,
- measurement of the hard chrome coating thickness,
- technical quality-control report.
What Should You Send for a Preliminary Assessment?
The information required depends on whether the enquiry concerns refurbishment of an existing roll or manufacture of a new component.
- Refurbishment: roll dimensions, photos and information about the existing coating.
- New roll: technical drawing.
Where Are Hard-Chrome-Plated Surfaces Used?
Coating requirements vary with the process. Abrasion resistance is critical in papermaking, while surface smoothness may be more important in printing or film production.
Moisture, Abrasion and Contact with Process Media
Rolls operate in environments involving moisture, mineral fillers and contact with doctoring elements.
- surface resistance to abrasion,
- operation in a humid environment,
- resistance to contact pressure and mechanical interaction.
Surface Precision and Low Roughness
In printing applications, geometry and highly precise finishing of the working surface are critical.
- high surface accuracy,
- low Ra surface roughness,
- possibility of a super-mirror finish.
Material Contact and Reduced Sticking
For rolls working with film, a smooth surface, low coefficient of friction and stable contact with the guided material are important.
- reduced material sticking,
- low surface friction,
- smooth guidance of film over the roll surface.
Operation Under Pressure and in Process Environments
Hard-chrome-plated rolls are used, among other applications, in dyeing lines and calenders, where the surface operates under pressure and in contact with process media.
- surface wear resistance,
- reduced fibre snagging,
- protection of the steel roll body surface.
What Should You Know About Hard Chrome?
Several hard chrome parameters are often oversimplified. In practice, the coating's intrinsic hardness, its behaviour at temperature and its conditional corrosion protection must be considered separately.
“Hard Chrome Is Always Corrosion-Resistant”
The coating protects the substrate as long as it remains undamaged. A natural network of microcracks and local damage may allow aggressive agents to reach the steel substrate.
Corrosion resistance must therefore always be assessed in the context of the specific operating environment.
“Hard Chrome Hardness Is Best Specified in HRC”
The intrinsic hardness of the hard chrome coating is specified on the Vickers scale: 850–1200 HV.
Rockwell testing of a thin coating may also reflect the influence of the substrate and give a misleadingly low result for the coating itself.
“Hard Chrome Retains Its Full Hardness Up to 400°C”
Full coating properties are maintained up to approximately 200°CBetween approximately 200–400°C hardness gradually decreases.
Approximately 400°C is the upper recommended temperature for continuous operation, but the coating hardness is already reduced at this temperature.
Microcracks Do Not Always Indicate a Defect
A fine, uniform network of microcracks is a natural feature of hard chrome structure and can contribute to lubricant retention.
It should not, however, be confused with wide mud cracking, which is a process defect and can lead to coating flaking.
Frequently Asked Questions About Hard Chrome Plating
Coating parameters are selected for the component and its operating conditions. Below we answer the most common questions asked before refurbishment or production of a new hard-chrome-plated surface.
What Is the Typical Hard Chrome Thickness?
The standard coating thickness range is 10–200 µm. Greater thicknesses are possible but require individual assessment and quotation 10–200 µm.
What Is the Typical Hardness of Hard Chrome?
The intrinsic coating hardness is typically 850–1200 HV. For thin coatings, Vickers microhardness is the appropriate assessment method 850–1200 HV.
What Surface Roughness Can Be Achieved After Hard Chrome Plating?
After polishing, the typical range is Ra 0.08–0.16 µmIn precision applications, a super-mirror finish of it is possible. Ra < 0,08 µm.
Up to What Temperature Can Hard Chrome Operate?
Up to about 200°C the coating properties remain practically unchanged. Between approximately 200°C and 400°C, hardness gradually decreases, so approximately 400°C is treated as the upper recommended temperature for continuous operation.
Does Hard Chrome Protect Against Corrosion?
Yes, but the protection is conditional. The coating protects the substrate as long as it remains undamaged. Through microcracks or local damage, aggressive media can reach the steel substrate and initiate under-coating corrosion.
What Materials Can Be Hard Chrome Plated?
Hard chrome can be applied to carbon steels, stainless steels and cast iron, among other materials.Surface preparation depends on the substrate material and its properties.
Can a Worn Roll Be Hard Chrome Plated Again?
In many cases, yes. The old coating can be removed electrochemically, after which the roll body geometry can be inspected and a new preparation and hard chrome plating cycle carried out. Refurbishment feasibility depends on the condition of the metal part.
Does Refurbishment Cover Only the Coating?
Not necessarily. Depending on the roll condition, the scope may also include mechanical work on journals, bearing seats, end plates or balancing so that the component is returned ready for further installation.
What Component Sizes Can Be Hard Chrome Plated?
The standard capability covers components up to approximately 600 mm, up to 6000 mm in length and up to 2500 kgin weight. Larger dimensions require an individual feasibility assessment.
What Should I Send for a Hard Chrome Plating Quote?
For refurbishment, the key information is a the roll dimensions, photos and details of the existing coating.For new manufacture, technical drawing is the basis for quotationtechnical drawing.
Do You Have a Component for Hard Chrome Plating or Refurbishment?
Send the basic information about the component. Based on it, we will assess the scope of work and select the appropriate process.
Information Needed for a Preliminary Assessment
- Refurbishment: component photos and basic dimensions.
- Information about the existing coating and where it is worn or damaged.
- New component: a technical drawing, if available.
- Information about how the component operates if it is relevant to surface selection.