Selecting the Right Material for Industrial Rubber Lining

Tanks, pipelines, valves, reactors, drums, and process equipment used in industrial facilities are often exposed not only to chemical corrosion, but also to severe operating conditions caused by the combined effects of abrasion, temperature, pressure, and mechanical stress.

For this reason, selecting the correct material for a rubber lining application cannot be based solely on rubber hardness or lining thickness. A successful lining system should be designed by considering the process fluid, chemical concentration, temperature, particle characteristics, flow velocity, operating pressure, equipment geometry, and service conditions as a whole.

Why Is Rubber Lining Used?

Although steel equipment provides high mechanical strength, it can suffer rapid surface degradation when directly exposed to many chemical and abrasive environments.

Rubber lining systems create a protective barrier between the steel surface and the process environment, helping to extend equipment service life.

The main purposes of rubber lining include:

• Protection against chemical corrosion
• Reduction of wear caused by slurry and solid particles
• Absorption of impact energy
• Prevention of direct contact between the metal surface and process fluid
• Extension of maintenance and refurbishment intervals
• Possibility of restoring the surface instead of replacing the entire equipment

Rubber lining is particularly important as an equipment protection method in industries such as mining, fertilizer, chemical processing, energy, metallurgy, and water treatment.

Abrasion and Corrosion Are Not the Same

One of the common mistakes in lining selection is treating abrasion and corrosion as the same problem.

Corrosion is the deterioration of a metal surface through chemical or electrochemical reactions.

Abrasion, on the other hand, is mainly the mechanical loss of material caused by solid particles striking, rubbing against, or moving at high velocity over a surface.

In the mining industry, these two effects often occur simultaneously.

For example, a slurry pipeline carrying ore, sand, or mineral particles may be exposed to both mechanical wear and chemical attack from the process liquid.

Therefore, selecting a lining solely for its chemical resistance may not be sufficient. The lining material must also provide suitable elasticity, hardness, and abrasion resistance.

Natural Rubber – NR

Natural rubber is widely used in applications requiring high abrasion resistance and elasticity.

In the mining industry, it may be used for:

• Slurry pipelines
• Cyclone connections
• Tanks
• Drums
• Mineral processing equipment
• Lines carrying solid particles

The elastic structure of natural rubber allows it to absorb a significant portion of the impact energy generated when solid particles strike the surface.

However, the chemical resistance of natural rubber is not suitable for every process. Alternative rubber types should be evaluated in environments containing acids, solvents, hydrocarbons, or elevated temperatures.

Bromobutyl Rubber – BIIR

Bromobutyl rubber is widely used in the chemical and process industries because of its low gas permeability and broad chemical resistance properties.

BIIR linings may be used in:

• Acid-containing tanks
• Chemical process equipment
• Reactors
• Pipelines
• Chemical storage equipment

One of the major advantages of bromobutyl lining systems is their ability to provide an effective barrier between the metal surface and many corrosive environments.

However, when evaluating suitability, not only the type of chemical but also its concentration and operating temperature must be considered.

Neoprene – CR

Neoprene, also known as chloroprene rubber, is an elastomer that provides balanced performance against oils, ozone, weathering, and various chemical environments.

For this reason, it can be used for both internal and external surface lining applications.

It may be considered particularly in applications requiring a combination of mechanical and environmental resistance.

Hard Rubber and Ebonite Systems

Ebonite is a rubber-based lining system with a high hardness level.

Unlike soft rubber linings, it has a more rigid structure and may be used particularly where a strong chemical barrier is required.

The performance of ebonite systems used in tanks, valves, pipelines, and chemical process equipment depends directly on:

• Rubber formulation
• Vulcanization conditions
• Lining thickness
• Surface preparation
• Adhesion system

Controlled vulcanization is of critical importance in ebonite applications.

How Is Lining Thickness Determined?

Greater rubber lining thickness does not always mean better performance.

When determining lining thickness, the following factors should be evaluated:

• Abrasion level
• Particle size
• Flow velocity
• Operating pressure
• Chemical environment
• Equipment geometry
• Expected service life

For example, a pipeline carrying a high concentration of solid particles may require a thicker lining than a tank exposed primarily to chemical attack.

However, unnecessarily increasing the lining thickness may create application difficulties and additional stress at joint areas.

Surface Preparation Is One of the Most Critical Stages of Rubber Lining

Even the highest-quality rubber material will not provide the expected performance if it is applied to an improperly prepared metal surface.

In industrial rubber lining applications, the steel surface is generally prepared by abrasive blasting.

The steel surface must be free from:

• Oil
• Rust
• Mill scale
• Old coatings
• Contamination

For many heavy-duty applications, surface preparation is carried out to Sa 2½ standard.

The objective is not merely to remove rust, but also to create a suitable surface profile for the adhesive system to achieve proper bonding.

Primer and Adhesive System

The bond between rubber and steel plays a critical role in the long-term performance of the lining.

Therefore, suitable primer and adhesive layers are applied after surface preparation.

The bonding system must be compatible with:

• Rubber type
• Vulcanization method
• Process temperature
• Chemical environment

Incorrect adhesive selection or contamination of the surface during application may lead to localized separation and eventual delamination of the rubber lining from the metal surface.

Vulcanization

Many rubber lining systems achieve their final physical and chemical properties through the vulcanization process.

Vulcanization may be carried out:

• Inside an autoclave
• Using steam
• Under controlled pressure and temperature
• Under atmospheric conditions in certain systems

Temperature, time, and pressure parameters must be determined according to the rubber formulation being used.

Insufficient vulcanization may prevent the lining from achieving the required hardness and mechanical strength, while excessive vulcanization may negatively affect the elastomer properties.

Joints and Detailing

A significant portion of rubber lining failures originate not from large flat surfaces, but from:

• Joints
• Flanges
• Nozzles
• Welded areas
• Sharp corners
• Geometrical transitions

For this reason, equipment should be designed and prepared to be as suitable as possible for rubber lining application.

Preparing sharp corners with appropriate radii, smoothing weld surfaces, and correctly forming lining joints directly affect the service life of the system.

Quality Control Tests

Visual inspection alone is not sufficient after completion of the rubber lining application.

Different quality control methods may be applied depending on project requirements.

Thickness Inspection

The lining is checked to verify that it complies with the thickness values specified in the project requirements.

Hardness Inspection

Rubber hardness may be measured using Shore A or another appropriate hardness scale for hard rubber systems.

This test can also provide useful information regarding the effectiveness of the vulcanization process.

Spark Test

The spark test, also referred to as an electrical continuity or holiday test, may be used to identify discontinuities in the lining surface.

The test voltage must be selected according to the lining system and its thickness.

The purpose is to detect small, visually undetectable discontinuities that extend through the lining to the metal substrate.

Visual Inspection

The lining surface is inspected for:

• Air bubbles
• Delamination
• Folding
• Open joints
• Surface deformation
• Mechanical damage

Where required, adhesion tests and test samples may also be included in the quality control plan.

Rubber Lining in Slurry Pipelines

Slurry transport is one of the most important application areas for rubber lining in the mining industry.

Solid particles contained in slurry can cause significantly higher wear, particularly at:

• Elbows
• Reducers
• Tee connections
• Areas where flow direction changes
• Points of high turbulence

For this reason, it should not be assumed that every section of a pipeline is exposed to the same level of abrasion.

When designing the lining system, pipe diameter, particle size, solids concentration, and flow velocity should be evaluated together.

Chemical Resistance Charts Alone Are Not Sufficient

The fact that a rubber material appears resistant to a certain chemical on a technical data sheet does not mean that it will be suitable for every process involving that chemical.

For example, the same chemical may affect rubber very differently at:

• 10% concentration
• 40% concentration
• 20 °C
• 80 °C

In addition, the process may contain more than one chemical component.

Therefore, the following information should be obtained whenever possible before selecting the lining material:

Chemical composition + concentration + temperature + pressure + solids content + flow velocity + service duration.

On-Site and Factory Application of Rubber Lining Systems

Rubber lining applications can be carried out both in the factory and on site.

In factory applications, equipment can be prepared under controlled conditions and, where suitable, vulcanized in an autoclave.

However, on-site application may be required for large tanks, fixed equipment, or systems that cannot be transported.

During on-site applications, the following parameters should be carefully controlled:

• Ambient temperature
• Humidity
• Dew point
• Surface temperature
• Dust and contamination

These parameters can directly affect the adhesion performance of the lining system.

Conclusion

Industrial rubber lining is much more than simply applying rubber to a metal surface.

A properly designed lining system requires the integrated management of:

process analysis, correct elastomer selection, surface preparation, primer and adhesive systems, controlled application, vulcanization, and quality control.

Especially in the mining and chemical industries, where operating conditions are severe, even minor application errors can significantly reduce lining service life.

At Ülker Linings, we determine industrial rubber lining systems by evaluating the specific process conditions of each piece of equipment. From surface preparation through final quality control, both factory and on-site applications are managed in accordance with technical procedures.

Our objective is not simply to line equipment, but to develop a protection system suited to the process conditions and thereby extend the service life of the equipment.