Friday, 27 August 2010

Using pH values to select car care products

Why pH values are not ideal criteria for the selection of car care products

Acidic and basic are two extremes that describe the chemical properties of a chemical. Mixing acids and bases can cancel out or neutralize their extreme effects. A substance that is neither acidic nor basic is neutral. The pH of distilled water is 7, this is neutral. Any solution with a pH below 7 is an acid and any solution with a pH above 7 is a base (alkali).

My point here is that, it is not possible to judge how well a product will do the job it is designed for just by measuring the pH and stronger is not always better. So, acid strength is always relative to the system you’re measuring and what materials are in danger of being dissolved or attacked by the acid pH is a measure of the relative strength of an acid but the key word is relative.
Some terms used to describe acids or basic

Neutralisation - a chemical reaction whereby an acid and a base react to form water and a salt; generally, the following occurs: acid + base → salt + water. Neutralization reactions are exothermic; giving out heat to the surroundings

Balanced pH - or neutral pH

Controlling pH - popular chemicals include calcium carbonate, calcium oxide, magnesium hydroxide, and sodium bicarbonate. The selection of an appropriate neutralization chemical depends on the particular application. pH controlled means it follows the major automotive manufacturer’s guidelines for exterior cleaners; the control limit being a pH 10.0<

Acids, Bases, and pH

There are several ways to define acids and bases, but pH only refers to hydrogen ion concentration and is only meaningful when applied to aqueous (water-based) solutions. When water dissociates it yields a hydrogen ion and a hydroxide.

Pure water is said to be neutral, with a pH close to 7.0 at 25 °C (77 °F). Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are said to be basic or alkaline.

An alkaline cleaner (hand soap has a pH of between 9.0 – 10.0) is used to clean most materials used in an automobile interior, including finished leather (leather is acidic by nature). Cleaning products use surfactants and other additives (such as water softeners) so its pH is not the only criteria used (i.e. a neutralized acid wheel cleaner has a pH of 7.0, so if pH is the only criteria it should be safe to use this product on anything as pH 7 (neutral)

Another reason for non-reliance of pH values when selecting products is the use of a buffer solution , this is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid, Citric acid is a useful component of a buffer mixture. It has the property that the pH of the solution changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications.

The main priority is to ascertain the material you are trying to clean and then select a chemical that is compatible to clean it with Providing the cleaning product selected is suitable, apply product to an applicator not the area to be cleaned (the only exception to this is glass surface cleaning) apply several drops of the selected cleaning solution in an inconspicuous area and rub gently with a clean, white micro fibre towel. Do not over wet. Use small amounts of the product and blot frequently, do not rub or use too much pressure. Do not use the product if it adversely changes the material’s colour or texture.

Although soap is a good cleaning agent, its effectiveness is reduced when used in hard water. Hardness in water is caused by the presence of mineral salts - mostly those of calcium (Ca) and magnesium (Mg), but sometimes also irons (Fe) and manganese (Mn). The mineral salts react with soap to form an insoluble precipitate known as soap film or scum. Soap film does not rinse away easily. It tends to remain behind and produces visible deposits on clothing and makes fabrics feel stiff. It also attaches to the insides of bathtubs, sinks and washing machines.

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