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High pH vs Low pH - Presoaks

The primary detergents responsible for getting the majority of the car surface clean have been given the general name of "presoaks". They are available in high and low pH. These detergents are applied and allowed to dwell in an effort to raise the dirt off the surface and be removed by high pressure or high volume rinse.

Chemically, presoaks are divided into two major groups, Low pH (Acidic) Presoaks and Alkaline (High pH) Presoaks. Each presoak has a specific role in removing organic or inorganic containments and can vary on the effectiveness depending upon their chemical make-up and nature of the soil to be removed. In general, Low pH Presoaks are most effective on mineral soils and Alkaline Presoaks are most effective on oily or organic soils.

Road film on cars always has some level of oily material in its content and therefore it is always necessary to use an Alkaline Presoak. When cleaning conditions are easy, a single application of an Alkaline Presoak is all that is necessary to get the job done. If the soils are thicker and have high oil content, a second application of the Alkaline Presoak will create best results. Alkaline Presoaks are formulated from a combination of alkaline builders and carefully selected surfactants (surface active agents) which when properly designed provide the fastest most effective cleaning without damaging the vehicle surface.

If soils contain a high mineral content, usually present as small clay particles, cleaning may be improved by the application of a Low pH Presoak. All Low pH Presoaks contain a type of acid. Some acids are better at attacking these mineral soils than others. The overall "acidic" strength of the solution is important, but the choice of acids and the surfactants used with them is what makes one Low pH Presoak better than another. The best formulations combine the proper acid ratios mixed with the most effective surfactants.

The one acid that we strongly caution against is Hydrofluoric Acid (HF). HF may be effective, but the level at which it becomes effective is also the level that it can do damage to vehicles, car wash equipment and people. Hydrofluoric Acid is very toxic and should only be handled by well trained and well informed people with the proper Personal Protection Equipment. Prowash makes sure that all our products are HF free. The International Carwash Association (ICA) has released a statement concerning their position of the use of HF. You can view their statement on their web site HERE.

At Prowash we have found that when using a Low pH I High pH two-step application process, the best results are when the Low pH product is applied first followed by the Alkaline Presoak with double the strength of the Low pH product. This is not a rule, however, some operators have found they get the best results by applying the Alkaline Presoak first. When both Alkaline and Acidic Presoaks are applied to the same surface, there is neutralization that takes place.

When one is applied, it combines with the dirt and then the second product is applied reacting with both the opposite presoak and the dirt, increasing the removal of dirt. The neutralization reaction in this instance is a benefit not a drawback.

Soils differ from place to place and time-to-time and it is important to keep this in mind. High/Low or Low/High and specific concentrations require experimentation and experience to determine the best application system to obtain the cleanest vehicles. Your chemical distributor can be the best resource for assistance as they have a broad range of experience with the products and the soils in your area.

Feel free to contact Prowash for the best advice and knowledge on presoaks.

Date Published: 16 January 2017