Passivation of Metal Surfaces
After cleaning, derusting, paint stripping, deoxidation or etching, metal surfaces can become particularly reactive. Passivation can improve the corrosion resistance of the surface and help protect it against renewed corrosion.
During passivation, a thin, stable protective layer forms on the metal surface. This layer acts as a barrier against external influences, making passivation an important part of industrial surface treatment and corrosion protection.
RHOBA-Chemie develops and supplies passivation agents for a range of materials, processes and industrial applications, including steel and cast iron as well as copper and brass.
What is passivation?
Chemical passivation involves treating a metal surface to form a thin, stable passive layer. This reduces the reactivity of the surface and can improve its resistance to corrosive influences.
Unlike conventional coating processes, passivation does not involve applying a separate paint or protective coating. Instead, it is based on the chemical modification or stabilization of the metal layer close to the surface.
What does a passive layer do?
A passive layer reduces the reactivity of the treated metal surface and can therefore improve corrosion protection. The level of protection achieved depends on factors such as the material, the passivation agent used and the specific process conditions.
Which metals and applications are suitable for passivation?
The appropriate passivation process and product depend on the material and the specific application. RHOBA-Chemie provides solutions for a range of metals and industrial processes.
Passivation of Steel and Cast Iron
Steel and cast iron components can be passivated following pretreatment such as cleaning, derusting or paint stripping. Passivation can therefore form part of the overall process for treating components and providing corrosion protection.
Passivation of Copper and Brass
Copper and brass can also be treated with suitable passivation agents. The selected product and process must be matched to the material, equipment and operating conditions.
Industrial Applications
Passivation agents are used in a range of industrial sectors, including:
- Automotive industry
- Aviation
- Paint shops
- Metalworking industry
- Defence industry
Passivation Agents from RHOBA-Chemie
RHOBA-Chemie offers a range of products for passivation and corrosion protection within the RHOBA SUPRA and RHOBA PURIA product lines.
Product | Type | Application |
| RHOBA SUPRA C303 | Multifunctional passivation concentrate for aqueous systems | Immersion, spray and spraying systems; passivation of steel and cast iron components; pressure-test water, water test tanks, leak testing and cooling circuits |
| RHOBA SUPRA C301 | Highly concentrated corrosion inhibitor and hardness stabilizer | Closed and semi-open cooling and process water systems; passivation of copper and brass |
| RHOBA PURIA Z202 | Special concentrate for neutralization and passivation | Passivation after descaling processes and applications requiring neutralization |
How is a metal surface chemically passivated?
The exact process depends on the material and the passivation agent used. An industrial passivation process can include the following steps:
1. Cleaning and degreasing
First, oils, greases, metalworking fluids and other residues are removed from the surface. A clean surface is essential for the subsequent treatment.
2. Pickling or further pretreatment
Depending on the condition of the workpiece, additional pretreatment may be required. Pickling, for example, removes oxide layers and other unwanted deposits from the metal surface.
3. Passivation
The passivation agent is then applied to the prepared metal surface. Depending on the product and process, this can be carried out by immersion or spray application.
4. Rinsing and drying
After passivation, the treated components can be rinsed and subsequently dried. The exact procedure depends on the product used and the requirements of the individual process.
Find the Right Passivation Agent for Your Process
Selecting the right passivation agent depends on several factors, including the material, pretreatment, application method and specific process conditions. A standard solution is therefore not suitable for every application.
Are you unsure which product is suitable for your application? Talk to RHOBA-Chemie. We will assess your requirements and support you in finding a suitable solution for your process.
Frequently Asked Questions About Passivation
When is passivation useful?
Passivation can be useful when a metal surface is particularly reactive after pretreatment such as cleaning, derusting, paint stripping, deoxidation or etching. For steel and iron components, for example, it can be used after paint stripping to protect the freshly treated surface against corrosion.
What is the difference between pickling and passivation?
Pickling chemically removes unwanted layers such as oxides, scale or other deposits from the metal surface. Passivation then acts on the prepared surface and improves its corrosion resistance.
Pickling and passivation therefore serve different purposes and can be consecutive process steps in industrial surface treatment.
Which systems can be used for passivation?
Depending on the product, RHOBA-Chemie passivation agents are suitable for immersion, spray and spraying processes. Which option is suitable for the respective process depends, among other things, on the product, material and system design.
How often does a metal surface need to be passivated?
This depends on the respective application and process. For components, passivation can, for example, be a defined process step after manufacturing or machining. In closed cooling water systems, on the other hand, corrosion protection can be maintained continuously using an inhibitor.
Are all passivation agents suitable for every material?
No. The passivation agent used must be suitable for the respective material and process. For example, RHOBA SUPRA C303 is only conditionally suitable for non-ferrous metals and aluminium. RHOBA SUPRA C301, on the other hand, must not be used in systems containing aluminium or aluminium-containing materials.