Those involved in anodizing have often encountered this problem: the same adjustable DC power supply works well for ordinary sulfuric acid oxidation, but when used for hard anodizing, the film becomes brittle and uneven in thickness; even with well-adjusted parameters, pinholes and color differences appear on a different batch of workpieces. The core issue isn't a faulty power supply, but rather the failure to match the correct power supply parameters to the characteristics of the anodizing process.
Anodizing processes are diverse, including ordinary sulfuric acid oxidation, hard anodizing, natural color anodizing, dyeing anodizing, and ceramic anodizing. Each process has different bath systems, film requirements, and workpiece materials, and the corresponding adjustable power supply parameters (current, voltage, waveform, ripple, etc.) also have specific requirements. Today, we'll break down the parameter matching logic for different processes in simple terms, allowing beginners to quickly get started, avoid detours, save on electricity costs, and improve yield rates.
First, clarify the core premise: the "three key aspects" of adjustable power supply parameters
Regardless of the anodizing process, before matching power supply parameters, grasp three core aspects: current density (determines film growth rate), voltage range (determines film thickness and density), and output waveform (determines film fineness). These three parameters directly affect film quality, production efficiency, and energy consumption, and are also the foundation for subsequent process matching.
Additionally: The ripple coefficient and load adaptive function of the adjustable power supply will also indirectly affect process stability, especially in precision anodizing scenarios, which will be discussed in detail later.
I. Ordinary Sulfuric Acid Anodizing (Most commonly used, suitable for aluminum profiles and hardware parts)
This is the most basic and widely used process. The core requirement is a uniform film with strong adhesion. It is mostly used for decorative or general protective applications. The bath solution is mainly sulfuric acid, and the temperature is controlled between 18-22℃.
Core Parameter Matching (Adjustable Power Supply Key Settings):
1. Current Density: 1.0-1.5 A/dm² (Crucial! Too low a current density results in slow film growth, while too high a current density can burn the film and cause pinholes);
2. Output Voltage: 12-18 V (Gradually increases with film growth, eventually stabilizing at around 15V to avoid rapid voltage increase at once);
3. Output Waveform: Pure DC (ripple coefficient ≤1%), no pulse required. A clean waveform reduces film pitting and improves gloss;
4. Operating Mode: Constant Current Priority (Ensuring uniform film growth rate and preventing uneven film thickness due to voltage fluctuations);
5. Additional Notes: The power supply must support soft start to avoid high current surges at startup that could cause film peeling.
Tip: If the workpiece surface has scratches, the current density can be appropriately reduced to 0.8-1.0 A/dm² to extend the oxidation time and improve film smoothness.
II. Hard Anodizing (Suitable for wear-resistant and corrosion-resistant applications, such as mechanical parts and molds)
The core of hard anodizing is the formation of a thick and dense oxide film (20-100μm thick). The bath solution is mostly a mixture of sulfuric acid and oxalic acid, and the temperature is extremely low (0-5℃). It places the highest demands on the power supply's load-bearing capacity and stability.
Core Parameter Matching (Key Adjustable Power Supply Settings):
1. Current Density: 2.0-3.5 A/dm² (Higher than ordinary oxidation to ensure film density, but requires a low-temperature bath; otherwise, the film may burn);
2. Output Voltage: 25-60 V (The thicker the film, the higher the voltage; it needs to be gradually increased, rising by 5V every 5 minutes to avoid sudden voltage spikes that could damage the film);
3. Output Waveform: Pulsed DC (duty cycle 30%-50%). Pulsed waveforms reduce heat generation, preventing film brittleness and cracking, while also improving film hardness;
4. Operating Mode: Constant current + constant voltage linkage (Constant current ensures growth rate in the early stages, constant voltage controls film thickness in the later stages to prevent excessive thickness leading to detachment);
5. Additional Notes: The power supply must have strong load adaptability. During hard oxidation, the bath impedance will continuously increase; the power supply output must be adjusted in real time to prevent current drops.
III. Natural/Dyed Anodizing (Suitable for decorative applications, such as electronic product casings and jewelry)
The core requirement for this type of process is a uniform, colorless film to facilitate subsequent dyeing or maintain the original color. The bath solution is typically dilute sulfuric acid, and the temperature is controlled at 20-25℃. Extremely high requirements are placed on power supply ripple.
Core Parameter Matching (Key Adjustable Power Supply Settings):
1. Current Density: 0.8-1.2 A/dm² (Lower setting to ensure a fine film layer and avoid rough surfaces that affect dyeing uniformity);
2. Output Voltage: 10–15 V, with stable output and fluctuation controlled within ±0.5 V. Even small voltage swings can result in noticeable color inconsistency on the anodized layer.
3. Output Waveform: Pure DC with ripple factor ≤ 0.5%. Ultra-low ripple is critical to prevent uneven dyeing and surface spots.
4. Operating Mode: Constant voltage mode is preferred. It ensures uniform film thickness and avoids uneven dyeing caused by overly thick or thin local areas.
5. Notes: The power supply must support high-precision adjustment. Fine resolution in current and voltage control helps avoid sudden changes that could destabilize the process.
IV. Ceramic Anodizing
(Ideal for insulation and stain-resistant applications such as medical devices and instrument housings)
Ceramic anodizing forms a dense, ceramic-like layer with outstanding insulation and anti-stain performance. It usually uses a boric acid–sulfuric acid bath and imposes high requirements on power supply precision.
Core Parameter Settings for Adjustable Power Supplies
1. Current Density: 1.5–2.5 A/dm², between conventional and hard anodizing levels to ensure a complete and effective ceramic layer.
2. Output Voltage: 20–35 V with stable output. Voltage fluctuations must be minimized to prevent uneven coating and spotting.
3. Output Waveform: Pure DC or low-frequency pulse (10–20 Hz). Low-frequency pulses help densify the ceramic coating and reduce pinholes.
4. Operating Mode: Constant current / constant voltage switching.
Constant current supports initial film growth; constant voltage ensures uniformity in the later stage. Typical process time: 30–60 minutes.
Notes: The power supply must be equipped with overcurrent and overvoltage protection. In case of any abnormality during oxidation, output should shut off immediately to prevent workpiece damage.
The key to matching power supply parameters to different anodizing processes is to figure out the current density, voltage range and output waveform. This is based on what the anodizing process needs to create the film and what the bath is like. For anodizing processes the adjustable power supply parameters need to be matched in a way that works for each process. The adjustable power supply parameters for anodizing processes are very important.
Don't blindly pursue high parameters; the right one is the best. If you're unsure which parameters to set for your process, YIBENYUAN adjustable anodizing power supply can provide customized parameter tuning suggestions to help you quickly find the optimal solution, saving electricity costs and improving yield.
Please do not hesitate to contact us.!
