Car Wash Chemistry
A Presoak is a one or two step cleaning process with two pH levels for different types of dirt. The low pH cleans chrome and glass, while the high pH cleans road film and paint surfaces. This process covers your vehicle with fast acting detergents that break down dirt and grime. This pre-soak process is specially formulated soap to gently loosen stubborn road film. Typically a low pH presoak is followed by a high pH presoak. A dwell time of 25 to 30 seconds for each soak is ideal.
Soaps/detergents – Remove Dirt from a Soiled Surface
- Detergents and soaps are used for cleaning because pure water can’t remove oily, organic soiling.
- Soap cleans by acting as an emulsifier. Basically, soap allows oil and water to mix so that oily grime can be removed during rinsing.
- Detergents were developed in response to the shortage of the animal and vegetable fats used to make soap during World War I and World War II.
- Detergents are primarily surfactants, which could be produced easily from petrochemicals. Surfactants (surface active agents) lower the surface tension of water, essentially making it ‘wetter’ so that it is less likely to stick to itself and more likely to interact with oil and grease.
- Detergents are similar to soap, but they are less likely to form films (soap scum) and are not as affected by the presence of minerals in water (hard water).
- Like soaps, detergents have hydrophobic or water-hating molecular chains and hydrophilic or water-loving components. The hydrophobic hydrocarbons are repelled by water, but are attracted to oil and grease. The hydrophilic end of the same molecule means that one end of the molecule will be attracted to water, while the other side is binding to oil.
- Neither detergents nor soap accomplish anything except binding to the soil until some mechanical energy or agitation is added into the equation. Rinsing washes the detergent and soil away.
Chelating Agents – Surround unwanted Metal Ions
- Chelating agents, (pronounced keelating from the Greek word claw) combines itself with disruptive metal ions in the water. The metal ions are surrounded by the claw-like chelating agent which alters the electronic charge of the metal ions from positive to negative (see diagram below.)
- This makes it impossible for the metal ions to be precipitated with the surfactants. Thus, chelated metal ions remain tied up in solution in a harmless state where they will not use up the surfactants.
- Some common chelating agents used in industrial cleaning compounds include phosphates, EDTA (ethylene diamine tetra acetate), sodium citrate, and zeolite compounds.
- The chelating process, though very effective, is not always necessary and adds to the cost of formulating detergents. Builders are often a good alternative.
Builders – softening, buffering, and emulsifying.
- Builders are added to a cleaning compound to upgrade and protect the cleaning efficiency of the surfactant(s).
- Builders soften waterby deactivating hardness minerals (metal ions like calcium and magnesium. They do this through one of two ways:
- Sequestration – holding metal ions in solution.
- Precipitation – removing metal ions from solution as insoluble materials.
- Builders, in addition to softening, provide a desirable level of alkalinity (increase pH), which aids in cleaning. They also act as buffers to maintain proper alkalinity in wash water.
- Builders help emulsify oily and greasy soil by breaking it up into tiny globules. Many builders will actually peptize or suspend loosened dirt and keep it from settling back on the cleaned surface.
- Three of the most common builders used in today’s heavy-duty detergents are:
- Phosphates, usually sodium tripolyphosphate (STPP), have been used as builders extensively in heavy-duty industrial detergents. They combine with hardness minerals to form a soluble complex which is removed with the wash water. They also sequester dissolved iron and manganese which can interfere with detergency.
- Sodium carbonate (soda ash) is used as a builder but can only soften water through precipitation. Precipitated calcium and magnesium particles can build up on surfaces, especially clothing, and therefore sodium carbonate is not used in laundry detergents.
- Sodium silicate serves as a builder in some detergents when used in high concentrations. When used in lower concentrations, it inhibits corrosion and adds crispness to detergent granules.
A Solvent is a substance, usually a liquid, capable of dissolving another substance.
- In addition to water, other chemical solvents are often added to cleaners to boost performance. Compounds such as 2 -Butoxyethanol (butyl), isopropyl alcohol (rubbing alcohol) and d-Limonene are all considered solvents. Their main function is to liquefy grease and oils or dissolve solid soil into very small particles so surfactants can more readily perform their function.
- During the winter months, organic solvents work to keep solutions from freezing because it acts to lower the temperature at which the mixture would normally freeze.
All Sealants & Drying Agents are based on the same chemical principal. Ingredients are formulated that will adhere to the vehicle, and make it repel water. The actual ingredients may vary from product to product, but the principal is the same.
- The purpose of a drying agent is to quickly make the surface of the vehicle repel water so it will run off the surface, leaving the car dry.
- The efficacy of drying agents is determined by how well the detergents are rinsed off the car, temperature of the surface and delivery water, drip space length/time, wind or blower action, and the cleanliness of the surface.
- A very low viscosity mineral seal oil may be used as a car wash drying agent.
- Sealant products are similar to drying agents in that they too should make water run off the surface, but they should also do more such as contain ultra violet light protection and special brighteners and provide extra protection for the surface.
pH Testing vs. Alkalinity Titration Testing
- Measuring the strength of alkalinity in a solution is called the “titration of the solution”, and a more accurate way to measure soap cleaning power.
- The difference between one measure on the pH scale, say from 8 to 9, will show 10 times as much alkaline charge! To get that much change, you would have to add several measures of product (liquid or powder).
- So, if you add more product into a soap solution, you will get more “power” from the soap. But remember, this may not change the pH of that solution by any measurable amount.
- The output is calculated by measuring a specified amount of a solution, coloring the solution with a dye, and then adding drops of acid to change the color of the solution. Titration of the solution is measured by the number of drops it requires to change the color of the sample. If it takes 10 drops to change the color, you then have a reference point to work with. Your mission is to find out where your car wash performs the best and make sure you maintain that reference point. It is important to test your soap solution mixture on a regular basis.
Contact a Chemloc representative
for alkalinity titration testing.