Phosphating of Metals
Phosphating is a chemical process used for the surface treatment of metals. During the process, the metal surface reacts with a phosphate-containing treatment solution to form a firmly adhering conversion coating made of metal phosphates.
Different phosphating processes are used depending on the material, the required surface properties and the subsequent process step. RHOBA-Chemie supplies specialty chemicals for industrial pretreatment and provides support in selecting and coordinating suitable processes.
What Is Phosphating?
Phosphating involves treating a metal surface with a phosphate-containing process solution. This produces a conversion coating consisting of insoluble metal phosphates. Depending on the process and equipment, phosphating can be carried out using immersion or spray application.
What Are the Benefits of Phosphating?
Phosphating prepares metal surfaces for subsequent processing. Depending on the process and application, the phosphate coating can:
- support corrosion protection
- improve the adhesion of paints and other coatings
- serve as a pretreatment before painting or powder coating
- absorb oils and lubricants
- prepare the surface for subsequent manufacturing and processing steps
A phosphate coating alone should not be considered permanent corrosion protection. Its effectiveness depends on the phosphating process and the overall coating or preservation system.
Phosphating Processes at a Glance
Common phosphating processes include zinc, manganese and iron phosphating. They differ in terms of the coating formed, its properties and its typical applications.
Zinc Phosphating
Zinc phosphating produces a crystalline zinc phosphate coating. It is commonly used as a pretreatment for subsequent coating processes, including in the automotive industry and vehicle manufacturing. A typical application is pretreatment before cathodic electrodeposition coating (CED), also known as e-coating.
Manganese Phosphating
Manganese phosphating produces a comparatively porous phosphate coating. The coating can absorb oils and lubricants, making the process particularly suitable for components where friction, wear and lubrication are important factors. Typical applications include gears, pistons and guides.
Iron Phosphating
Iron phosphating produces a thin conversion coating. The process is commonly used as a pretreatment before painting.
Applications of Phosphating
Phosphating is used in a wide range of industrial sectors, including:
- Automotive industry
- Aviation
- Paint shops
- Mechanical and plant engineering
- Metalworking industry
- Furniture industry
- Defence industry
Pretreatment Process
Phosphating is usually part of a multi-stage pretreatment process. The individual process steps are coordinated with the material, equipment and subsequent application.
A typical process may include:
- Cleaning and Degreasing: Oils, greases and other contaminants are removed from the surface.
- Pickling or Derusting: Where required, oxide layers and rust are removed.
- Phosphating: The metal surface is treated with a phosphate-containing process solution to produce the required conversion coating.
- Rinsing: Residues from the previous process step are removed.
- Post-treatment: Depending on the process and subsequent application, an additional treatment may be required.
- Painting or Powder Coating: The required coating is then applied.
RHOBA SUPRA – Process Chemicals for Phosphating
The RHOBA SUPRA range includes products for cleaning, degreasing, derusting and phosphating metal surfaces.
Produkt | Typ | Einsatzbereich |
| RHOBA SUPRA V101 | Concentrate for degreasing, derusting and phosphating | Combined cleaning and phosphating of light metals and ferrous materials |
| RHOBA SUPRA V102 | Concentrate for degreasing, derusting and phosphating | Combined degreasing and phosphating, including pretreatment of iron and steel before painting and powder coating |
| RHOBA SUPRA V103 | Phosphoric acid-based multifunctional product | Combined degreasing and phosphating using spray, immersion or high-pressure application |
Phosphating with RHOBA-Chemie
Selecting the right process chemical depends on more than just the material. Equipment, application method, required coating properties and subsequent process steps also need to be taken into account.
RHOBA-Chemie supports customers in selecting and coordinating suitable products and in optimizing existing phosphating processes. Our services include:
- Customized solutions for different process requirements
- Laboratory analysis for process optimization and troubleshooting
- Technical support in selecting and optimizing pretreatment processes and chemicals
- Consulting on cleaning, degreasing, derusting and phosphating
The Right Phosphating Process for Your Application
Not every process is suitable for every material or system. The preceding cleaning process as well as the subsequent coating or preservation process also need to be considered when selecting a phosphating system.
RHOBA-Chemie supports you in selecting suitable specialty chemicals for your phosphating process and coordinating the individual process steps.