Alkaline detergency is a deep cleaning process, mainly suitable for removing scale, greases and oils. Usually finds application on ferrous and galvanized materials.
How does it work
The detergents are made up of strong alkaline raw materials, such as soda and potash, products well known for being very active in the removal of organic pollutants and difficult dirt such as waxes and fats. The effectiveness is also assisted by surfactants whose function is to remove and emulsify the oils. Obviously the cleaning power has increased considerably from the temperature, therefore the detergent bath in systems is kept at at least 50 ° C. This process can only be used on non-oxidized surfaces, and it is not recommended to use it for metals such as aluminum since hydroxides react quickly with it generating hydrogen. In order to use it on aluminum, you need to be careful, using specific processes or using less concentrated alkaline charges. Other unsuitable materials are bronze and brass, which can be affected, especially on coloring.
A properly performed alkaline detergent cycle can guarantee optimal pre-treatment for preparation for painting. It can be carried out by means of only three steps: Cleaner - Rinse - Rinse, but it is recommended to add a final passivation to increase the adhesion of the paint. A classic example of passivation that is becoming increasingly widespread is nanotechnology, which usually requires a further final rinse of demineralized water.
Examples of formulation
As already mentioned, the most important component of the alkaline formulations are the bases, that is potash or soda. The concentrated product can contain more than 50% of potash (usually supplied at 50%), the remaining components can be other reinforcing bases, such as amines, sodium metasilicate, bicarbonate or other salts and also the sequestrants should not be missing, which they allow to dilute the product in hard water. The most widely used sequestering agents were certainly EDTA and salts such as sodium gluconate, a large quantity of innovative molecules or polymers with enormous chelating power are now well established. The detergents can also contain surfactants, in the case of single-component products. Given the high caustic percentage, keeping performance surfactants inside the formulation could be complex, therefore it is often preferred to add mixtures of these to the product diluted in the tank. The selection of surfactants in alkaline detergents is important as the foam in a washing tunnel, due to the saponification of the oils, could reach harmful levels for the process and the plant.