As with any manufacturing process, the final performance of parts produced using MIM (Metal Injection Molding) technology largely depends on the integration of various post-processing operations, such as heat treatments or surface treatments applied after forming.
Surface treatments not only modify the aesthetic appearance of the parts but also improve critical properties such as wear resistance, friction, corrosion protection, and thermal fatigue strength This is vital for enabling MIM components to be used in demanding applications—from the automotive and biomedical industries to precision tools, electronic devices, and high-performance equipment.
At Alfa MIMtech, we integrate all stages of the design, development, and manufacturing process for any MIM project, managing the surface treatments applied to our products in order to deliver a completely finished part to the customer.
1. BALINIT (PVD/PACVD coatings such as TiN)
Characteristics:
BALINIT coatings are obtained through physical vapor deposition (PVD) or plasma-assisted chemical vapor deposition (PACVD), forming thin layers of titanium nitride and other compounds These layers provide high surface hardness, significantly reduce the coefficient of friction, and offer outstanding resistance to wear, corrosion, and oxidation—even under demanding conditions.
Advantages:
- Significantly extends the service life of MIM components.
- Enables the use of parts in high-performance applications such as cutting tools, medical components, and precision automotive parts.
- Reduces maintenance needs due to low friction and high durability.
- Promotes more stable and efficient operation of mechanisms using treated parts..
2. BICOAT (Anti-friction coating)
Characteristics:
BICOAT is a dry-film coating composed of solid lubricants embedded in a resin matrix, similar to a bonded lubricating paint. This layer is particularly effective in boundary friction conditions where other lubricants lose effectiveness, protecting the part against wear, corrosion, and dirt buildup while reducing noise and preventing “stick-slip” in mechanical motion.
Advantages:
- Provides continuous protection even under severe service conditions.
- Reduces maintenance by eliminating the need for frequent oil or grease lubrication.
- Ideal in environments where liquid lubricants are impractical or prohibited.
- Ensures smoother and quieter operation of assembled mechanisms.
3. CERAKOTE (Thin-film ceramic coating)
Characteristics:
CERAKOTE is an advanced ceramic coating designed to resist abrasion, wear, and chemical corrosion. It can withstand extreme temperatures ranging from 600 to 980 °C (depending on the series), preventing thermal fatigue, oxidation, and deformation of parts exposed to intense heat. It also offers excellent UV stability and hydrophobic properties that repel moisture and dirt.
Advantages:
- Increases durability in harsh or demanding environments.
- Expands the use of MIM components in aerospace, energy, and defense sectors.
- Reduces failures caused by heat and corrosion, extending replacement intervals.
- Enhances the visual appeal of parts, available in various finishes and colors.
4. ZINC PLATING (Electrolytic zinc coating)
Characteristics:
Zinc plating is an electrolytic process that deposits a uniform zinc layer on the metal surface. This coating acts as cathodic protection, sacrificing itself to preserve the base steel or alloy against oxidation. It can be applied in different finishes—white, yellow, or black—to meet specific aesthetic or functional requirements.
Advantages:
- Cost-effective method for protecting MIM steel parts from oxidation.
- Provides good protection in moderately corrosive environments.
- Enhances the appearance of parts with uniform finishes.
- Compatible with a wide range of geometries and sizes.
5. CHROME PLATING (Decorative or hard)
Characteristics:
Chrome plating consists of applying a metallic chromium layer that can be decorative—with a bright, reflective appearance—or functional as hard chrome. Beyond its aesthetic value, this treatment increases surface hardness, improves wear resistance, and provides effective protection against corrosion and abrasion under intensive use.
Advantages:
- Greatly enhances mechanical and chemical resistance of the surface.
- Hard chrome plating is ideal for high-friction parts, extending their lifespan.
- Decorative chrome adds aesthetic value and prestige.
- Compatible with high-precision MIM-manufactured parts.
PHOSPHATING
Characteristics:
Phosphating is a chemical treatment that produces a layer of metallic phosphates bonded to the surface. While not a protective coating on its own, its main function is to serve as a base for subsequent paint or oil layers, offering mild corrosion resistance when combined with suitable sealants.
Advantages:
- Improves adhesion of paint or additional coatings.
- Provides slight corrosion resistance when used with oils or sealers.
- A fast, cost-effective method to prepare MIM parts.
- Facilitates painting or further finishing, ensuring greater durability.
7. SHOT BLASTING
Characteristics:
Shot blasting is a mechanical process in which abrasive particles are projected at high speed onto the surface of the part. This removes burrs, residues, and impurities while generating a uniform texture, often producing a matte finish. It also prepares the surface for subsequent coating applications.
Advantages:
- Optimally prepares surfaces for further treatments (painting, nickel plating, ceramic coatings).
- Improves adhesion of subsequent layers.
- Can relieve surface stresses and improve fatigue strength in some cases.
- Cost-effective and suitable for various part sizes and complexities.
8. ULTRASONIC CLEANING
Characteristics:
Ultrasonic cleaning is a deep-cleaning process that uses high-frequency sound waves in a liquid medium to create cavitation. This phenomenon effectively removes dirt, oil, grease, and machining residues—even from internal cavities or hard-to-reach areas—without altering or damaging the original metal surface.
Advantages:
- Provides deep, uniform, and reproducible cleaning.
- Essential for preparing parts before applying high-quality coatings.
- Ensures removal of contaminants that could affect adhesion or performance
- Especially useful for MIM parts with complex geometries.
9. NICKEL PLATING
Characteristics:
Nickel plating involves depositing a metallic nickel layer either electrolytically or through autocatalytic chemical processes. Chemical nickel plating offers the advantage of a uniform coating even on complex geometries. The result is a surface with high resistance to corrosion, wear, and abrasion.
Advantages:
- Excellent for complex geometries typical of MIM.
- Provides an attractive, bright finish.
- Serves as a base for other coatings (e.g., chrome or paint).
- Extends part life in aggressive environments.
10. BLACK OXIDE (Bluing)
Characteristics:
Black oxide is a controlled oxidation process that forms a thin black oxide layer on steel surfaces. It is a low-thickness treatment that does not significantly alter part dimensions and provides limited corrosion protection, while offering an aesthetically pleasing, uniform dark finish.
Advantages:
- Provides a professional dark appearance.
- Economical and quick to apply.
- Offers added protection when combined with protective oils.
- Commonly used for mechanical parts and firearms due to its simplicity and appearance.
11. PAINTING (Liquid or powder)
Characteristics:
Painting involves applying a liquid or powder coating to the metal surface, the latter using electrostatic techniques. In addition to offering corrosion protection and moderate wear resistance, it provides extensive aesthetic versatility with a wide range of colors, textures, and finishes.
Advantages:
- Highly versatile in terms of aesthetics and function.
- Allows customization with specific colors and finishes.
- Adds extra protection against environmental factors.
- Cost-effective and suitable for large MIM production runs.
12. POLISHING
Characteristics:
Polishing is a mechanical finishing process that removes irregularities, smooths roughness, and creates a smooth, shiny surface. The result is an improved aesthetic appearance that enhances product quality while facilitating cleaning and preparing the part for subsequent treatments.
Advantages:
- Enhances the visual value of components.
- Reduces surface friction, improving performance in some applications.
- Simplifies cleaning and maintenance.
- Serves as a preliminary step for coatings requiring smooth surfaces.
13. SUR SULF (Surface sulfurization)
Characteristics:
The SUR SULF treatment is a thermochemical process that forms a layer of iron sulfide on the steel surface. This modification significantly reduces surface friction, increases wear resistance, and provides additional corrosion protection by acting as an integrated solid lubricant.
Advantages:
- Acts as a built-in solid lubricant.
- Ideal for moving components such as gears or bearings.
- Extends service life under high-friction conditions.
- Reduces the risk of seizure in mechanical systems.
14. VIBRATORY FINISHING
Characteristics:
Vibratory finishing is a mass-finishing process in which parts are placed in a vibrating container with abrasive media. The constant motion produces controlled contact that removes burrs, smooths edges, and evens the surface, allowing efficient treatment of large batches of parts simultaneously.
Advantages:
- Cost-effective method for finishing large volumes of MIM parts.
- Ensures uniform finish across all treated parts.
- Improves aesthetics and prepares surfaces for further treatments.
- Adjustable for different intensities (fine or aggressive finish).
Conclusion
Surface treatments are a key factor in maximizing the benefits of the MIM process, as they allow parts to be tailored for specific industrial uses—enhancing mechanical and chemical resistance, as well as appearance and functionality.
The choice of treatment depends on application requirements:
- For high wear and friction: BALINIT, BICOAT, or SUR SULF.
- For corrosion resistance: Nickel plating, Chrome plating, Cerakote, or Zinc plating
- For aesthetic purposes: Painting, Polishing, or Black oxide.
- For surface preparation: Shot blasting, Vibratory finishing, or Ultrasonic cleaning.
Thanks to this wide range of solutions, MIM-manufactured parts can compete in the most demanding applications, extending their service life and improving overall performance.
