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Two Step - New Dance or Smart Way to Clean Cars?

What does two step or one step cleaning refer to?

Two step cleaning refers to the use of two pH extremes in presoak application, typically, an acid presoak followed by the application of an alkaline presoak. Recall high school chemistry: anything that has a pH of 7 (like water) is neutral, anything higher than 7 is alkaline and anything lower than 7 is acidic.

Why Use Two vs. One?

The answer is soil solubility or soil removal. Certain soils will not dissolve or release in alkaline conditions and vice versa. With most soils, 90% or more will loosen and let go in the presence of alkaline conditions. Soils that are removed easily in alkaline conditions are dirt, pollen, oily soils and bugs. Look in the other products around you, and you will see many examples of this. Dishwasher detergents are very alkaline, and laundry detergent is also alkaline. Deck and siding cleaners also share this alkaline nature. Alkaline conditions, the higher end of the pH scale, provide chemical "heat" that tends to dissolve, loosen and prepare soils for blasting by a high pressure step in the cleaning process.

But do we want a car that is 90% clean? NO. Most operators are challenged (especially in touchless applications) to get the vehicle as clean as possible. So what do you do about some of the soils that still cling desperately to the surface of the vehicle? This is where you apply a low pH, the opposite of a high pH, to the soils. Soils soluble in acid conditions are mineral scale and some clays. Examples of low pH products in our lives are mineral cleaners, lemon juice, coca cola and specialty cleaners.

Should I be scared of the word acid? It sounds dangerous ...Low pH products can sometimes be thought of as "dangerous" but, as mentioned earlier, any of these products can classify as acidic if they vary at all from the neutral pH of 7. No one would consider drinking a Coke very dangerous while in fact the strength of that acid rivals many acidic presoaks! Typically, both alkaline and acidic presoaks are 80 to 100 times weaker as applied compared to their stock or concentrated solution strength.

There are some dangerous acids that some companies use trying to push the level of cleaning higher and higher. There is a product sometimes used called Hydrofluoric Acid or HF. HF is used to significantly raise the impact that the acid has on stubborn road films and scale. It is highly effective, but, unlike many phosphoric or sulfuric acid-based products, it is extremely hazardous and needs to be handled with well trained and informed users. Additionally, a significant amount of PPE (Personal Protective Equipment) needs to be used in the presence of this product. This product has the further disadvantage of being hard on the equipment in and around its use so this could be a faster way to equipment replacement and reduced parts life.

What if I only can use one or the other?

Some machines were not designed or built for two step cleaning, and, in other cases, customers want to keep it simple and use only one. If you had to choose only one presoak to use, you would be well-advised to only use the alkaline form of a presoak vs. an acidic presoak. The alkaline presoak, as mentioned earlier, will remove the widest form of soils vs. the specialized nature of the acid presoak.

Why do most operators use a low pH first and then a high pH?

The most common way to apply a low pH presoak is to apply it first. The reason behind this is that the cost and strength of an acid presoak dictates that you must put it on first. It is cheaper to have the alkaline presoak cover over the acid and move the pH all the way from low to high. This has to do with the cost and availability of alkaline ingredients compared to acid ingredients. You could, in theory, apply the alkaline first, and, if you used enough acid, you could push the acid conditions to recommended levels; however, this is more costly. There is an advantage to doing this if you want to add a rinse (to first remove the alkaline) or money is not an object. A vehicle with a low pH surface tends to take waxes and drying agents better. This is the reason that many tricolours on the market today have a low pH or slightly low pH nature to them- to help ensure that the surface of the vehicle has all alkaline levels eliminated.

Solving your problems and making recommendations at your site

Most operators shudder at the thought of figuring out their car wash chemistry. They often get confused on alkaline and acids even after hearing over the years about the difference between acids and alkali. It is important when setting your detergents that you are dealing with a knowledgeable and educated representative. There are many car washes operating today who have inadequate levels of these opposite chemistries, and their cleaning performance is paying the price. The operator is also paying the price as they may be spending their monies simply neutralizing the first presoak without ever entering the alkaline stage of cleaning. Be sure you are dealing with an expert who understands and is measuring the relative strengths of both followed by comparing to some manufacturer recommended setting. A small difference in the case of two step cleaning can make a huge difference.

If you’re unsure or want some assistance getting your car wash chemistry right, contact our friendly soap technicians here at Prowash on 03 8340 3200

Date Published: 11 July 2017