Use of Paint in Dipping Tanks
The application of paints by dipping can be a fast and efficient method of paint applications. There are, however, a number of factors to consider when choosing this method of application, viz.
Choice of Paint
Not all industrial paints are suitable for dipping, for example, some are prone to skinning in the dipping tanks. It is important, therefore, to contact our Technical Service Department for advice on suitability of paints.
Dipping Tank Design
The design of the tank must take into account the size and shape of the object to be dipped and the rate of throughput anticipated. It must be decided whether the goods will be dipped manually, by hoists, or by continuous conveyors.
Circulation of paint in the tank should be carried out manually by mechanical stirrers or by circulation pumps with in line filters, to prevent settling. The system should not be so vigorous as to raise the temperature of the paint and cause solvent evaporation. To prevent aeration of the paint, recirculating systems should be so designed that the return paint re-enters the tank at the top, but below the surface of the paint. The surface flow of paints should such as to prevent bubbles forming at the point of entry and exit of the dipped articles. All dipping tanks should be covered when not in use to prevent solvent loss. An area should be formed for the painted objects to be drained off before stoving or air drying.
Fire and Fume Hazards
The large volume of paint held in tanks presents a potential fire hazard. The tanks should be locked away from all possible sources of ignition. Where necessary, flameproof electrical equipment should be installed. Adequate fire fighting equipment should be at hand. The fumes given off by the paint should be extracted to a safe area. It is preferable to isolate the dipping process from other areas of the factory.
Strict control on quality of paint is essential if a good finish and long life for the paint is to be achieved. Care should be taken to keep all foreign matter, e.g. rags, swarf, away from the tanks.
The viscosity of the paint should be below 40 seconds when measured with a Size 4 Flow Cup to BS.3900 Part A.6 at ambient temperatures. Viscosity testing equipment is available from Laboratory Equipment Suppliers. Over-thinning of the paint will result in poor gloss and covering: it will eventually cause a breakdown of the paint structure which cannot be rectified.
Samples of paint drawn from the dipping tanks may be submitted to our Laboratories for testing at regular intervals when a full report will be given.
Design of Articles for Dipping
Articles that are to be dipped should, if possible, be designed to reduce areas where runs or sags may occur. All pockets should have drain holes, sharp edges should be avoided, to prevent pigment tearing. Holes may become blocked, and gaps and threads bridged.
We trust this information sheet assists you in achieving good results, when using dipping paints and dipping tanks. If you should require any further information, then please contact our Technical Service Department.