REDARTI Column-Variac Aluminium Colouring Rectifiers are heavy-duty power systems designed specifically to meet the precise voltage and current needs of the electrolytic colouring (electro-colouring) processes applied after anodic oxidation in aluminium anodizing plants. Thanks to the pure column-variac regulation architecture, homogeneous and spot-free deposition of metal salts (tin, nickel, copper, etc.) into the porous structure of aluminium profiles and sheets is guaranteed.
Our systems are built with 3 different cooling options — air-cooled (A), water-cooled (W) or oil-cooled (O) — according to the plant's infrastructure. They are manufactured at a standard operating voltage of 25V over a wide capacity range, from sensitive technical parts up to 50 A to huge industrial production lines up to 30,000 A. Depending on user preference, the display interface is available as a digital LCD panel or a Siemens PLC-based colour touchscreen (HMI).
Our units are produced in two separate topologies according to the application: AC-only operation or hybrid DC/AC operation. The system uses a column-variac system with glass-fibre (daglas) insulated electrolytic copper windings and the Siemens PLC-based CDC-101 / RED+ CCP automatic colour control panel. The result is smooth current-voltage regulation from 0% to 100% with zero harmonic distortion and a pure sine output signal, completely eliminating shade differences (Delta E) between batches.
The Critical Role of the Column Variac in Electrolytic Colouring
In an aluminium colouring bath, metal deposition at the barrier layer depends directly on the quality of the applied waveform. The technical advantages of the column-variac architecture:
- Continuous, Undistorted Pure Sine Waveform: The column-variac system adjusts the pure sinusoidal waveform of the mains frequency steplessly without any harmonic distortion, so metal deposition at the base of the pores is smooth and homogeneous.
- Linear, Smooth Voltage Regulation from 0% to 100%: Thanks to the carbon brushes moving on the column variac and the servo/inverter motor drive, millimetric, ramped voltage adjustment from 0V to 25V is achieved without voltage jumps. Sudden current shocks at the start of colouring are prevented and the bath barrier layer is fully protected.
- Heavy-Duty Durability & High Energy Efficiency: Thanks to glass-fibre (daglas) insulated electrolytic copper windings and an M5 0.30 silicon-steel core, no additional heating or harmonic losses occur under overload and 24/7 continuous operation. A 96% power factor (Cos φ = 0.96) and an overall efficiency above 93% are achieved at full load.
The Importance of DC/AC and AC-Only Operation in Electro-Colouring
In aluminium anodizing processes, colouring quality depends directly on the barrier at the base of the pores and on the structure of the metal deposit. The advantages offered by our production types:
- AC-Only Operating Mode (Standard Sinusoidal Electro-Colouring): The basic method that ensures consistent deposition of tin (Sn) or nickel (Ni) into the aluminium pores. During the negative half-cycle of the sine wave, metal ions are deposited at the pore base, while during the positive half-cycle overheating and breakdown of the barrier layer are prevented. It offers a high-yield, economical solution for light bronze, bronze and champagne shades.
- DC/AC Operating Mode (Advanced Pre-Modification & Dark-Shade Process): In this electrochemically superior method, direct current (DC) is applied to the bath for a set time and voltage before AC colouring. The DC preparation phase homogenises the thickness of the barrier layer at the pore base and prepares the active surface. The ramped AC stage that follows then achieves spot-free colouring that penetrates fully to the pore base and is 100% repeatable between batches, even in difficult shades such as dark bronze, black and stainless steel.
Key Features
- Column-Variac Technology: Linear, harmonic-free voltage/current adjustment from 0% to 100% without chopping the mains sine wave.
- Versatile Cooling Architecture: Heavy-duty air-cooled (A), water-cooled (W) or oil-cooled (O) versions tailored to plant conditions.
- Wide Current Range (50 A - 30,000 A / 25V): Fully suited to everything from special technical parts up to 50 A to huge industrial colouring lines up to 30,000 A.
- Flexible Display Interface: Digital LCD panel or Siemens PLC-based colour touchscreen (HMI), as the user prefers.
- Selectable Operating Topology: AC-only operation for standard applications or advanced DC/AC operation for spot-free, dark shades.
- Siemens PLC-Based CDC-101 / RED+ CCP Automatic Colour Control: 6 steps per program and a 50-recipe memory; bath temperature monitoring, stepped and ramped operation.
- High Efficiency and Power Factor: 96% full-load power factor and >93% system efficiency thanks to electrolytic copper windings and M5 silicon steel.
- Advanced Water and Safety Hardware Package: Water-flow switch, water-pressure measurement system, high-pressure water circulation manifold, transformer and variac over-temperature sensors, fast-acting fuses and a phase protection unit.
Applications
- Aluminium Profile Electro-Colouring Plants: Colouring of architectural façade profiles and door/window systems in tin- and nickel-based baths.
- Aluminium Sheet and Component Colouring Lines: Colour coating of sheets, façade cladding panels and aluminium accessory parts.
- Dark-Shade and Black Anodizing Applications: Lines producing spot-free, high-contrast dark bronze and black finishes in DC/AC mode.
- Technical and Defence Surface Finishing: Colouring of special aluminium parts requiring high light and corrosion resistance.
