Factors Influencing the Electroplating Process of Galvanized Steel Coils

Introduction

Galvanization, the process of electroplating steel with zinc, involves electrolyzing Zn2+ ions from a zinc solution, depositing them onto the steel surface to form a uniform and dense layer of zinc metal. Zinc, being amphoteric, readily dissolves in both acid and alkali, making it more prone to electrolysis in a solution. The electroplating process comprises pre-treatment, electroplating, and post-plating processes, with the quality of the coating depending on the material’s electroplating process.

Several factors influence this process, summarized as follows:

  1. Zinc Purity

Higher purity in zinc blocks results in a narrower brightness range, making it easier to achieve thicker coatings with lower iron content, especially beneficial for automotive panels.
Lower purity zinc may have a wider brightness range, requiring more time to achieve the specified zinc layer thickness, leading to higher iron content in the galvanized layer.

  1. Sodium Hydroxide Concentration

Sodium hydroxide has a dual impact on the reaction. Excessive concentrations can lead to scorching during high-temperature operations.
Insufficient concentrations reduce solution dispersion, compromising the quality of the zinc layer.

  1. Iron Content

Elevated iron content results in a higher presence of iron in the coating, leading to inadequate brightness of the passivation film.
Low iron content reduces the corrosion resistance of the galvanized layer, resulting in an olive-green tint on the surface of automotive panels.

  1. Brightening Agent

The common brightening agent, a blend of ZF-100A and ZF-100B, requires careful control of concentration. High concentrations enhance coating brittleness, while low concentrations may cause sparse coatings in low-current areas, leading to uneven passivation

  1. Temperature

Elevated temperatures during electroplating reduce solution dispersion, increase iron content in the coating, and result in uneven passivation.
Lower reaction temperatures may lead to scorching in areas with high current density, causing increased coating brittleness and slower deposition rates.

  1. Cathode Movement Speed

Ensuring a continuous movement of the cathode is crucial. Excessive speed may result in rough coatings in high-current density areas.
Slow movement may generate airflows, causing uneven coatings on the material.

Understanding and controlling these factors play a pivotal role in optimizing the electroplating process for galvanized steel coils, ensuring high-quality coatings that meet the diverse requirements of various industries. Contact us for more!