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Before deciding on the best cleaning method, clean several relatively small areas to assess the efficiency of the method and the appearance and condition of the surface after cleaning. The reasons for cleaning must be considered carefully because results with methods intended to improve only the appearance of the surface can differ substantially from results obtained with methods intended to prepare the surface for a heavy-duty urethane or epoxy coating.
Dirty, Oily, Contaminated Concrete
One of the most common problems facing the floor painter is the cleaning of dirty / contaminated concrete. Areas around machinery, pumps and equipment subject to heavy spillage of oils and other contaminants should be closely inspected.
It is important to realise concrete is like a sponge – it is full of air holes. Pour a bucket of water onto any unsealed concrete floor and you will watch almost the entire amount simply disappear. Being water, this will simply rise and evaporate over the following few days until the concrete reverts to a completely dry state. However, when oil or some other form of contamination has penetrated the concrete, this will never ‘evaporate’. Furthermore, it must be realised that a chemical clean will only wash the top surface. Due to the fact that the oil has penetrated into the concrete, as the surface is cleaned, the oil remaining within the slab will simply rise to the freshly cleaned surface and for the floor only to appear as dirty ‘now’ as it was immediately prior to cleaning!
It is advised to degrease the surface and then to check the soundness of the surface structure. Should the concrete have been damaged or weakened by such contamination, mechanical removal of the damaged surface is paramount.
A similar cleaning procedure or just steam cleaning with hot detergent will clean tight, old coatings. All loose and peeling paint must be removed prior to the application of any further coating.
Testing Procedure
The following procedures can be used to determine a suitable chemical preparation method.
Treat several small areas (approx. 1sq.m) with Polycote Etch IT. A mixture of 1 part Etch IT to 3 parts water is recommended for testing. If the solution bubbles vigorously producing a uniform white foam or haze of bubbles and leaves a clean surface, there is no curing membrane or hardener.
Should a single etch result in the surface being appreciably rougher than fine sandpaper, repeat the test with a more dilute acid solution until an etched profile similar to fine sandpaper is obtained.
However, if the opposite happen whereby only a weak or partial reaction occurs, beware of the fact that a curing agent or surface hardener is present. In many cases, more than one etch is required. A poor result and/or failure of the above tests indicates the presence of a hardener, which cannot be removed chemically. Remove concrete to a depth of at least 1-3mm, preferably with the use of a heavy diamond grinder or scabbler.
When diluting acid with water, always add acid to water.
Previously Painted Surfaces
It is extremely important to ensure the existing surface is completely sound and never more so than when painting over an existing floor coating.
Too many people would like to simply re-coat the floor with little to no preparation. However, should the existing coating be peeling, flaking or bubbling, it must be realised that to simply coat
over a product that has not fully adhered to the substrate is nothing more than a complete waste of time, effort and money!
Testing Procedure
For the removal of existing paints and epoxy coatings, most companies will favour mechanical cleaning such as Vacuum Assisted Diamond Grinders and / or Vacuum Assisted Shotblasters.
However, if the job is only small and/or the conditions not allow such methods, then chemical preparation will be required.
For the removal of standard single pack paints and linemarking, use Polycote Graffiti Remover Liquid. For heavy painted surfaces or areas coated with twin pack paints, the use of Polycote Graffiti Remover (Twin Pack) Gel is advised. Scrub a small area with non-woven abrasive and the chosen stripper. Remove paint and rinse thoroughly with a cleaner to neutralize.
Once completed, it is often advisable to etch the surface as well with Polycote Etch IT, as this will not only neutralize the paint stripper but will also give the perfect treatment to the concrete and ensure a good adhesion to the resultant surface.
CAUTION: Wear protective clothing, gloves and goggles and, if necessary, respiratory protection when performing these tests.
FURTHER TECHNICAL HELP REQUIRED?
Thank you for your interest and we hope you have found the above information both interesting and helpful. However, should you still have be unsure as to the best solution for your needs, please don’t hesitate to ring our technical helpline now on 01234 846400. We have a fully qualified team ready to give practical advice and help assist you as much as possible.