What causes the blackening of the edges of sulfamate nickel holes?

What causes the blackening of the edges of sulfamate nickel holes?

Wed Mar 13 08:43:09 CST 2024

The nickel sulfamate plating process is a plating technique that employs sulfamic acid as the primary nickel source, and is used to produce high-purity, low-internal-stress nickel plating layers, especially for applications that have stringent requirements on the mechanical properties of the plating. However, some problems may be encountered during the plating process, such as blackening of the sulfamate nickel layer at the hole edges. The reasons for this can be manifold, some common causes and corresponding solutions are listed below:

1. Excessive current density:

Excessive localized current densities may result in excessive accumulation of nickel at the edge of the hole, producing overburning and leading to blackening. The solution is to adjust the cathode current distribution to reduce the current density, or use specially designed spreaders and shielding to adjust the current distribution.

2. Plating solution composition imbalance:

If the concentration of nickel sulfamate in the plating solution is not appropriate, or if heavy metal impurities are present, contamination and blackening of the plated layer may result. The plating solution composition should be analyzed and maintained regularly, and filtration systems and ion exchange resins should be added to remove impurities as necessary.

3. Poor flow and mixing conditions:

In the nickel sulfamate plating process, insufficient agitation or liquid flow may lead to uneven plating solution composition in localized areas, and hydrogen bubbles are not easily removed, affecting the quality of the plated layer. Enhanced agitation and optimized liquid flow can improve plating uniformity.

4. Inadequate pretreatment of the substrate:

Improper surface pretreatment can lead to inadequate plating adhesion and inclusion of impurities, which can result in blackening. Ensure that the workpiece passes through appropriate cleaning, degreasing, pickling and activation steps to improve the bonding of the plating to the substrate.

5. Presence of organic pollutants

Organic contamination, such as grease, can cause uneven plating and may form localized black spots. Organic contamination can be minimized by maintaining good plant sanitation and using decontaminants.

The solution to the problem of blackened edges of nickel sulfamate plated holes, in addition to troubleshooting the causes listed above, requires the use of Bigely nickel sulfamate additive Ni-1000, which can be added to the plating solution to obtain a semi-glossy, low-stress, ductile coating.

If you are interested in nickel sulfamate additives, please feel free to contact us!