What is an Etch Primer?
Binding of etch primer with the substrate is achieved by combining an acid with the paint so that the acid microscopically etches the surface of the substrate, thus forming a physical and chemical bond between the two.
Ferrous or non ferrous metals, fibre glass and resin mouldings
- Single pack
- Two pack
Single Pack Etch Primers
Single pack, as its name suggests is a one part Etch Primer where the activating acid is already combined with the paint. The advantage of Single Pack Etch Primer is, that apart from stirring, it is ready to be applied by brush to your substrate. The disadvantages of Single Pack Etch Primers is that because they already have the acid in, they have a shelf life, this life is about 12 months from the date of manufacture (NOT from the date of purchase) for this reason all Single Pack Etch Primers manufactured carry a best before end (BBE)
date on the can Single Pack Etch Primers are only suitiable for Non Ferrous metals and fibre glass / resins. They do not have enough
acid in them to etch steel and cast iron.
Single Pack Etch Primers can be sprayed, either with an airbrush or spray gun, But in order to spray single pack etch satisfactorily it must be thinned about 50:50 with etch primer thinners and sprayed at a pressure of 10 psi or below .
Two Pack Etch Primers
Two Pack Etch Primers are supplied in two parts – the Primer and an acid based accelerator.
Metal rods should be avoided to mix the primer and accelerator.
The advantages of two pack etch primer:
- the ability to use the same product on both ferrous and non ferrous metals
- the ease of spraying and brushing
- better shelf life
Applying Etch Primers
Only the thinnest coat is required and a second coat is not neccesary.
Etch Primers only start to work after they are dry. It is therefore beneficial to only use the thinnest coat possible.
Once applied the Etch Primer needs to be left to dry, both to allow the etching process to work and to allow the evaporation of the solvents contained within the paint.
All Etch Primers need to be left for a minimum of 24 hours at a temperature of 18 – 20 degrees celcius to dry properly.
Whilst this is the minimum it is advisable to allow significantly longer before applying topcoats.