Car wash chemistry - high vs. low pH presoak

Car washing might seem like a relatively straightforward affair, but when you look at the chemistry involved it is incredibly complex.

Presoaks are divided by pH. There are low pH presoaks (below 7), which are acidic, and high pH presoaks (above 7), which are alkaline. Cars drive around and gather a layer of soils comprised of: sulphur compounds, greases, salts, bugs, bird droppings, etc. When these soils are left untreated they can slowly damage a vehicle’s clearcoat. Removing this road film is critical to prolonging the life of a vehicle’s surface. Low pH presoaks help by removing inorganic soils (non-living things like salt and sand), while the high pH presoaks help by removing organic soils (living things like bugs, greases, bird droppings, etc). When used together they create a 1-2 punch.

And, as you know, the strength of the presoak can be adjusted depending on the chemical composition of the soils involved. So when do you choose a high pH presoak vs. a low pH presoak or both?

When to use a high pH presoak

Considered the most used car wash chemical, high pH presoaks are comprised of alkaline builders and surface active agents (surfactants). When combined, these builders and surfactants help to remove and emulsify organic material (bugs, bird droppings, oils, greases, etc), while effectively neutralizing any acid that may be on the vehicle’s surface.

Road film usually has an oily composition, making it the ideal material for an alkaline detergent to remove. If the oily build up/road film on the car is not too bad, just one application is all that’s needed to get your client’s car back to pristine condition. Should the soils be thicker and with a higher amount of oil, additional applications may be required.

ChemQuest offers a variety of high pH presoak products, one of which is our Select 35: A highly concentrated, heavy duty alkaline detergent with multiple applications as a touchless presoak, tire cleaner, and wheel cleaner for both touchless and friction automatics and conveyors. Designed with the latest technology in road film removal, this product produces cleaner and shinier glass, paint, wheels, white walls, raised letters, and black tires.

When to use a low pH presoak

Low pH or acidic presoaks are great at removing granular and inorganic road film. When the soil is of high mineral composition, your best bet is to apply a low pH presoak because of its acidic properties, which are effective at getting rid of these tiny clay particles. While the acidic strength of a low pH presoak is crucial, the determining factor of an effective one is getting the types of acids and surfactants. On that note: a titration kit is an ideal tool for measuring the concentration of your presoak.

Sometimes they work best together

In general, acidic presoaks are best utilized by combining them with an alkaline presoak in a two-step application process. Acidic presoaks attack inorganic road film, especially the glass, wheels and lower parts of the car. An alkaline presoak follows this to help remove greases, oils, bugs, and bird droppings over the rest of the vehicle. Additionally, it helps neutralize any remaining acidity left on the vehicle.

Use ChemQuest products for the best of both worlds

The low/high pH debate has merits on both sides. ChemQuest takes the heat out of the debate by analyzing your car wash needs and creating wash systems that work for you.

Deciding on the pH level required is just part of the solution to getting a customer's car into perfect — clean — condition. For over 25 years, ChemQuest has prided itself on cutting through the complex chemistry to make products that work consistently and effectively, whatever your customer’s needs. Our focus on long-term partnerships with dedicated business support and customer service are what help our valued partners.

Get in touch with us and let’s talk car wash and everything in between.

For more information on the products and services we offer, please head over to our website: www.carwash-soap.com