Choosing the best surface treatment: a guide to electrolytic and chemical plating
Summary: Electrolytic vs. Chemical Plating
Electrolytic plating uses external current and is suitable for rapid deposition, though thickness may vary on complex geometries. Chemical (electroless) plating utilizes an autocatalytic reaction for absolute uniformity across all surfaces. Precision manufacturing requires accounting for these coating thicknesses—often between 5 to 20 microns—during the CNC machining phase to maintain strict engineering tolerances.
Functional differences between electrolytic and chemical plating
The selection between electrolytic and chemical (electroless) plating is a fundamental decision that dictates the performance and dimensional accuracy of a component. Electrolytic plating relies on an external electrical current to reduce metal ions from a solution onto the substrate. This process is highly effective for applications requiring specific decorative finishes or rapid deposition. However, the nature of electrical current leads to uneven distribution; the coating tends to accumulate more heavily on sharp edges and external corners—areas of high current density—while recessed features and internal bores receive significantly thinner layers. In contrast, chemical plating, such as electroless nickel, operates through a controlled autocatalytic chemical reaction. Because no external electricity is used, the metal ions are deposited with absolute uniformity across every surface the solution touches. This characteristic is indispensable for complex geometries where functional tolerances must be maintained within microns throughout the entire part. For a contract manufacturer, understanding the behavior of these processes is essential to ensuring that the coating enhances the part’s properties without compromising its mechanical intent.
How does coating thickness impact the tolerances of precision parts?
In high-precision CNC machining, the coating is never a superficial addition; it is a dimensional component of the final geometry. When tolerances are defined at the level of hundredths of a millimeter, a standard industrial coating can easily push a part out of specification if not accounted for during the initial machining phase. For example, a 10-micron nickel layer increases the external diameter of a shaft by 20 microns and decreases the internal diameter of a bore by the same amount. Managing this "buildup" requires seamless communication between the machining and plating departments. At Valtimo, we treat surface treatment as an integral part of the manufacturing chain. This means the pre-plating dimensions are calculated specifically to allow for the thickness of the chosen coating. To verify these results, we employ X-ray-based surface thickness measurement and Coordinate Measuring Machines (CMM). This rigorous quality control ensures that even after complex multi-stage plating, the component fits perfectly into its final assembly, maintaining the tight tolerances required by the defense and aerospace industries.
CNC Machining
Precision milling and turning services where pre-plating dimensions are calculated to meet final tolerances.
Material requirements for medical devices and demanding electronics
The medical technology and electronics sectors operate under some of the world’s most stringent material standards. Components in these fields often require a combination of high electrical conductivity, corrosion resistance, and biocompatibility. Surface treatments like gold and silver plating are common, but the technical execution of these processes is what determines the long-term reliability of the device. In medical equipment, coatings must withstand aggressive sterilization cycles and constant cleaning without degradation or leaching of harmful substances. In electronics, the focus is often on signal integrity and contact reliability. Traditional gold plating often utilizes cobalt as a hardening agent, which can introduce magnetic properties or impurities that are undesirable in sensitive high-frequency applications or specific medical environments. To address these demands, we utilize the Ronovel N process for gold plating. This method is entirely cobalt-free, providing a high-purity gold layer that meets the strictest technical requirements while aligning with modern environmental and health standards. By utilizing such specialized processes, manufacturers can ensure that their components remain stable and functional over thousands of duty cycles in the most demanding operational environments.
Why choose cobalt-free gold plating for industrial components?
In precision engineering, the choice of a hardener in gold plating is not merely a chemical detail; it is a critical functional decision. Traditional industrial gold plating often utilizes cobalt to increase hardness and wear resistance. However, for high-frequency electronics and sensitive medical sensors, cobalt can introduce unwanted magnetic properties and potential bio-incompatibility. At Valtimo, we address these technical challenges by utilizing the Ronovel N process for gold coating. This cobalt-free method produces a high-purity gold layer that maintains excellent contact resistance and solderability without the risks associated with alloyed impurities.
For the defense and aerospace sectors, where signal integrity and reliability are paramount, this high-purity gold coating ensures that components operate consistently across their entire lifecycle without interference from magnetic residues. Furthermore, the absence of cobalt aligns with the strict purity requirements of the medical technology industry, where components often come into contact with sensitive biological environments or require non-magnetic properties for use in imaging equipment.
Navigating REACH compliance and PFAS restrictions in surface treatment
The regulatory landscape for industrial coatings is undergoing a significant shift, driven by the European Chemicals Agency (ECHA) and the proposed universal restriction on per- and polyfluoroalkyl substances (PFAS). As many traditional fluoropolymer-based coatings face phase-outs or strict derogations, manufacturers must transition to REACH-compliant alternatives that do not sacrifice performance. Navigating these changes requires a partner who understands the chemical compositions of modern plating solutions and can provide documentation to prove compliance.
At our production sites in Valtimo and Pattijoki, the focus is on sustainable and compliant production. This commitment is reflected not only in the choice of chemistry but also in our energy footprint, as we utilize 100% renewable energy in our manufacturing processes. By selecting a coating partner that is already aligned with future environmental standards, companies in the medical, defense, and technology sectors can future-proof their supply chains. This proactive approach avoids the risks of sudden material obsolescence, costly redesigns, and the logistical hurdles associated with non-compliant components in the European market.
Surface Plating
Technical nickel, cobalt-free gold, and REACH-compliant chemical treatments for demanding industries.
Managing the production chain from machining to final assembly
The technical value of a precision component is realized when the entire manufacturing sequence—from the initial CNC-machining to the final functional coating and subsequent assembly—is managed as a single, cohesive process. When these stages are fragmented across multiple suppliers, the risk of tolerance stacking, logistical delays, and communication errors increases. By integrating CNC-milling and turning with specialized surface treatments under one ISO 9001:2015 certified quality management system, we ensure that the coating thickness is accurately accounted for from the very first tool path.
This holistic management model extends to mechanical, electronic, and fine-mechanical assembly. Once the parts have been machined and coated to the exact specification, they are moved directly to assembly, where kitted components are integrated into finished sub-assemblies or turnkey products. For the customer, this vertical integration eliminates the burden of coordinating multiple vendors and ensures a transparent chain of custody for quality and documentation. Whether it is a small test series or a large-scale annual contract, managing the entire chain from a single source provides the predictability and cost-efficiency required in today’s high-tech industries.
Assembly Services
Full-service mechanical and electronic assembly from test series to serial production.
