Improving Bonding Ability of Plating
The electroplating layer provides strong adhesion to the substrate and imparts corrosion resistance, wear resistance, solderability, and many other desirable properties for the treated part. Plated coatings are particularly suited for decorative finishes since they are bright, durable, and highly uniform. However, a lack of understanding of electroplating processes can lead to plating defects, often in the form of poor bond strength or adhesion. With knowledge of how electroplating works, understanding the fundamentals of plating chemistry and techniques, and following proper plating procedures, it is possible to ensure strong bonding and optimal coating performance.
Why is Bond Strength Important?
Bond strength is a measure of the strength of the attachment between the plated coating and substrate. The adhesion of the coating to the substrate must be strong enough to withstand various mechanical and environmental forces. Weak adherend bonds can lead to chipping, pitting, flaking, and corrosion of the plated coating.
Factors Affecting Bond Strength
Adequate bonding between the substrate and the plated coating depends on numerous factors.
Substrate Prep: Substrate surface preparation is a critical step in achieving strong bonding between the substrate and the plated coating. The surface of the substrate should be clean and free of contaminants such as oils, dirt, corrosion, and oxides. This is particularly important when plating over stainless steel or other corrosion-resistant alloys.
Polarity: Different substrates require different voltage polarities in order achieve good bonding. For example, aluminum must be plated using a negative charge while most other ferrous metals, including stainless steel, should be plated with a positive charge.
pH level: The plating solution pH can also affect bond strength. For best performance, the pH should generally be in the range of 6.5 to 9.5.
Anode-to-Cathode Ratios: The ratio of anode to cathode area is another important factor in achieving optimal bond strength in electroplating. The goal should be to have the anode area equal the cathode area, as this will ensure maximum coverage and uniformity in the deposited coating.
Cleaning: Cleaning the substrate prior to electroplating is also important for achieving good bond strength. In some cases, additional cleaning and/or post-plating treatments may be necessary in order to optimize the bond between the coating and substrate.
Types of Plating
The type of plating used can also impact the bond strength of the finished part. Nickel plating is a common choice for good bonding, as it provides a strong, corrosion-resistant coat of metal. Copper plating is also effective, as it helps to improve wettability and promote good adhesion between the substrate and the coating.
Conclusion
Good bonding between the plating layer and the substrate is a critical factor in achieving optimal performance of electroplated parts. Although there are many variables that must be accounted for when plating, with proper understanding and execution of the plating process, it is possible to ensure strong bonding and optimal coating performance.
