The metal surface should be thoroughly cleaned (remove oil, oxidised skin, etc.), otherwise it will easily lead to leakage of plating or poor bonding.
Author: Anna
I. Material factors
Substrate quality: The purity and surface condition (e.g. oxide film, crease, pit, etc.) of the metal substrate directly affect the adhesion and uniformity of the plating layer.
Zinc ingot purity: the purity of zinc in the zinc solution and the content of impurities (such as lead, iron, aluminium, etc.) will affect the gloss and corrosion resistance of the coating.
II. Process parameters
Pre-treatment: The metal surface should be thoroughly cleaned (remove oil, oxidised skin, etc.), otherwise it will easily lead to leakage of plating or poor bonding.
Current density: too high current density will lead to roughness of the plating layer, too low will result in slow deposition speed, affecting the thickness of the plating layer.
Plating solution composition:
Zinc ion concentration: too high leads to increased brittleness of the plating layer, too low is too thin;
Additives: such as insufficient brightener will lead to poor dispersing ability and uneven plating layer;
Sodium hydroxide concentration: too high is easy to scorch the plating layer, too low is poor conductivity.
Time and temperature:
Too short a time to thin plating, too long may cause coarse crystallisation;
Temperature should be controlled in a reasonable range (e.g. 435-460°C at room temperature or 500°C at high temperature), too high leads to increased zinc consumption, too low affects the deposition rate.
Operating parameters: dip plating time (0.5-2 minutes), lifting speed (e.g. 1.5 metres/minute) need to match the size of the workpiece to ensure uniformity.
III.Equipment and Environment
Conductive system: poor conductivity will lead to uneven current distribution, local plating layer is too thin.
Workpiece design: workpiece hanging method, and anode spacing is unreasonable may cause shielding effect or plating thickness difference.
Environmental control: After passivation, if the environment is humid or contains corrosive media, it is easy to trigger white rust (zinc oxidation).
IV. Post-treatment
Passivation process: improper passivation solution composition and process will lead to the film layer is not bright or corrosion resistance decreased.
Cooling treatment: cooling speed and water quality (including surfactants) affect the surface finish of the coating.
V. Other factors
Workpiece characteristics: high-carbon steel, cast iron and other materials precipitation of hydrogen is serious, reducing current efficiency.
Human operation: such as tying too close, current estimation error and other process control errors.
The above factors need to be systematically managed through the whole process of quality control (including material inspection, process monitoring, post-treatment inspection, etc.)