What is the difference between alkaline and acidic cleaning agents?

Alkaline and acidic cleaning agents differ in their composition, applicable scope, cleaning principles, effects on materials, and safety, as detailed below:

1. Composition

Alkaline cleaning agents: The main components are alkaline substances such as sodium hydroxide, sodium carbonate, and sodium silicate. They may also contain surfactants and chelating agents to enhance cleaning effectiveness.

Acidic cleaning agents: The main components are acidic substances such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and citric acid. They may also contain corrosion inhibitors and surfactants.

2. Applicable Scope

Alkaline cleaning agents: Suitable for removing oil, grease, protein, dust, and light rust from some metal surfaces. Commonly used for cleaning metal materials, industrial equipment, kitchenware, and clothing. They are also widely used in the textile and food processing industries.

Acidic cleaning agents: Primarily used to remove scale, rust stains, oxides, and some alkaline dirt. Commonly used for cleaning bathroom fixtures, kitchen scale, and rust stains on metal products. They are also frequently used in industrial processes requiring the removal of metal oxide scales.

3. Cleaning Principle

Alkaline cleaning agents: Utilize the saponification and emulsification effects of alkaline substances to decompose oily dirt into water-soluble substances. The alkaline environment also helps remove some acidic dirt and dust. Surfactants reduce the surface tension of water, allowing the cleaning solution to better wet the surface of the object, improving cleaning efficiency.

Acidic cleaning agents: Through chemical reactions between acids and alkaline substances such as scale and rust stains, insoluble salts and metal oxides are converted into water-soluble substances, thus achieving the purpose of removing dirt. Corrosion inhibitors reduce the corrosion of the metal substrate while removing dirt.

4. Effect on Materials

Alkaline cleaning agents: Most metal materials have good tolerance, but amphoteric metals such as aluminum and zinc may be corroded at high concentrations or with prolonged contact. The impact on plastics and rubber is relatively small, but some strongly alkaline cleaning agents may cause some alkali-resistant plastics and rubber to age or deform.

Acidic cleaning agents: They are highly corrosive to metal materials, especially active metals such as iron, zinc, and aluminum, which are easily corroded by acids. Therefore, corrosion inhibitors are usually added when cleaning metals. Acidic cleaning agents will also corrode some carbonate stones, such as marble and limestone, causing loss of luster and pitting.

5. Safety

Alkaline cleaning agents: High concentrations of alkaline cleaning agents are corrosive and can cause harm to skin and eyes. Protective equipment should be worn during use. Ingestion can cause serious damage to the digestive system.

Acidic cleaning agents: Acidic cleaning agents are generally more corrosive than alkaline cleaning agents and can cause serious burns to skin and eyes. Volatile acidic gases have an irritating odor and can harm the respiratory system if inhaled. In addition, mixing acidic cleaning agents with certain substances (such as metal powders and alkaline substances) may cause violent reactions or even explosions.

6. Post-Cleaning Treatment

Alkaline cleaning agents: After cleaning, it is generally necessary to thoroughly rinse with clean water to remove residual alkaline substances and prevent subsequent effects on the cleaned object. If the discharged cleaning wastewater is highly alkaline, neutralization treatment is required to meet environmental discharge standards.

Acidic cleaning agents: Similarly, thorough rinsing with clean water is necessary to prevent residual acid from corroding the surface. Treatment of acidic wastewater usually requires the addition of alkaline substances for neutralization, and it may also be necessary to treat pollutants such as heavy metal ions in the wastewater through sedimentation and filtration to meet environmental requirements.