Queensland Electroplating Pty Ltd (QE) is a small electroplating factory specialising in the tin plating of bus bars for electric transformers. Small quantities of plating of other metals, such as gold and silver, are also carried out, but because of the toxic heavy metals involved, no chrome plating is done. QE is a company owned and run by an environmentally caring family. In an industry that is highly competitive, they recognise that any wastage which causes pollution can also detract from their operating profits. Hence, it is in their business interest to avoid or minimise wastage wherever possible.
The basic equipment comprises of a container filled with water, with a small amount of acid or alkali added to improve its conductivity, and two poles (anode and cathode) installed on opposite sides of the solution.
Application of a direct current across the solution causes the migration of positively charged particles (anions) towards the negative electrode (cathode), and negatively charged particles (cations) towards the positive electrode (anode). The process depends to some degree on the concentration of acid or alkali in the solution, and also on the temperature and the voltage applied across the poles.
In the case of electroplating, the object to be coated plays the role of the cathode, and the coating substance, the anode. The coating substance can sometimes be in liquid form added to the solution and subsequently dissociated into anions and cations, which can be coated onto the plates.
In the electroplating industry, the wastage of chemicals has always been a problem. The nature of the process inevitably results in a certain amount of 'drag-out' of chemicals as they are removed from the plating solutions. The solutions may contain acids, caustics or heavy metals such as cadmium, chromium or lead. If these drag-outs are allowed to drip to the floor, they may not only end up in the storm water system causing pollution, but also result in wastage of valuable chemicals.
When addressing this issue, the staff decided to look at the entire process and totally redesign their production line in accordance with cleaner production methods. Where available technology was unsuitable or inadequate, it was redesigned or modified to meet the sponsors' requirements.
Eleven polyurethane tanks were purchased and placed 'in line' to save time in the plating process.
All jobs are pre-cleaned with rags to improve the life of the cleaning solution, before being hung from racks with copper wire. The racks are suspended from a crane arm attached to an electric winch.
The first two tanks contain cleaning fluid, and are heated to 70 0C. These tanks are fully insulated to save heating energy and to keep the factory cool. The surfaces of these tanks are covered with Choffles, or floating insulation pillows, to minimise evaporation and heat loss.
The next tank contains a caustic solution for cleaning. Submersible filters in the caustic tank extend the life of the chemicals, and because they are fully contained within the tank, there is absolutely no chance of spillage from split pipes or bad connections.
The following acid tank neutralises any caustic residues and is also internally filtered.
The next two tanks contain rinsing water. They use a cross flow rinsing technique, which allows the final rinse water to be reused as initial rinse when it becomes contaminated. This saves water and reduces discharge to trade waste.
In the plating tanks, bus bars and other conductors are plastic coated to improve their lifespan. The chemical composition of the solution is monitored regularly.
The process is finished off with several more rinses. These tanks also use the cross flow rinsing technique to minimise water usage and discharge to the sewer.
All racks are given a good shake to dislodge any liquid whilst still positioned over the tank. This simple procedure saves a great deal of the solution used. To further minimise wastage, drain boards fit between all the tanks to divert any drippings back to the respective tanks, saving raw materials and minimising pollution from spillage of chemicals and rinse water.
At the end of the process, the copper wire hooks are collected for recycling by a licenced scrap metal dealer.