How to Prepare an Effective Industrial Acid-Based Cleaner: A Step-by-Step Practical Guide

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Acidic cleaning agents play a key role in industrial cleaning, especially where it is necessary to remove inorganic impurities such as limescale, rust, or mineral deposits. Their effectiveness depends not only on the selection of the right acid but also on its concentration, temperature, and additional additives that improve wetting or inhibit corrosion. Incorrect preparation, however, can lead to material damage, reduced effectiveness, or safety risks. This guide will show you how to proceed step by step to achieve optimal results without compromising safety.

1. Selecting the Appropriate Acid and Its Concentration

The foundation of every effective industrial acid-based cleaner is the correct choice of acid according to the type of contamination and the material to be cleaned. To remove inorganic deposits such as limescale, rust, or metal oxides, mineral acids are most commonly used – for example, hydrochloric acid, sulfuric acid, or phosphoric acid. Hydrochloric acid is highly effective against calcium and magnesium deposits but is aggressive toward metals, so it is recommended for cleaning ceramics, glass, or stainless steel. Phosphoric acid is gentler on materials and is often used for derusting steel or cleaning surfaces before painting.

The concentration of the acid is crucial for achieving the desired effect without damaging the material. Generally, solutions with a concentration of 5–20% are used for industrial applications, where higher concentrations accelerate the reaction but increase the risk of corrosion. Hydrochloric acid is often used as a 10% solution, while phosphoric acid can be used up to 20%. It is always necessary to verify compatibility with the material and comply with safety regulations under REACH and CLP, including proper labeling and handling.

2. Addition of Corrosion Inhibitors and Stabilizers

Acid-based cleaners can damage metal surfaces if used incorrectly, so it is essential to add corrosion inhibitors. These substances form a protective layer on the material's surface and slow down or completely block the reaction of the acid with the metal. Commonly used inhibitors include organic compounds such as thiourea, benzotriazole, or inorganic salts like sodium nitrate. The choice of inhibitor depends on the type of acid and material – for example, benzotriazole is effective for copper and its alloys, while thiourea protects steel and cast iron.

Stabilizers play a crucial role in extending the shelf life of cleaning agents. Acidic solutions can degrade or lose effectiveness over time, especially during storage. By adding chelating agents such as ethylenediaminetetraacetic acid (EDTA), the precipitation of metal ions is prevented, and the stability of the solution is maintained. The dosage of inhibitors and stabilizers typically ranges from 0.1–2% of the total volume, with the exact amount needing to be verified through laboratory tests for the specific application.

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3. pH Optimization and Addition of Surfactants

The effectiveness of an acidic cleaning agent strongly depends on its pH, which should be adjusted to the type of contamination. To remove mineral deposits, a pH range of 1–3 is typically used, while for organic dirt, a slightly higher pH (3–5) may be more suitable. Precise pH adjustment is carried out using pH meters or indicator papers, and by diluting with water or adding more acid if necessary. It is important to remember that excessively low pH can increase the aggressiveness of the agent and damage the surface.

Surfactants improve the wetting and penetration of the cleaning agent into layers of dirt. Anionic surfactants, such as alkyl sulfates or alkylbenzene sulfonates, are effective in removing grease and organic contamination, while non-ionic surfactants (e.g., ethoxylated alcohols) enhance foam stability and compatibility with various materials. The dosage of surfactants typically ranges between 1–5%, and their selection should consider both effectiveness and ecological and safety requirements under the REACH regulation.

4. Testing, Safety, and Practical Applications

Before deploying a cleaning agent in operation, it is essential to conduct laboratory tests on material samples and contamination. Standard test methods verify the effectiveness of dirt removal, material compatibility, and solution stability. Tests should include measuring material weight loss, visual surface assessment, and analysis of residual contamination. If necessary, adjustments to the composition are made, such as changing the acid concentration or type of inhibitor.

Safety when working with acidic cleaning agents is a priority. It is necessary to use personal protective equipment (gloves, safety goggles, respirators) and ensure adequate ventilation of the workspace. According to the CLP regulation, the agent must be properly labeled with warning symbols and safety instructions. During application, it is recommended to follow the technological procedure – for example, applying the agent with a brush, spray, or by immersion, while observing the recommended exposure time (usually 5–30 minutes). After cleaning is complete, the surface must be thoroughly rinsed with water and any acid residues neutralized, for instance with a sodium bicarbonate solution.

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Selecting compatible additives to enhance efficacy and stability

Acidic cleaning agents often require the addition of specific additives that enhance their performance and extend their shelf life. Among the most commonly used are chelating agents, which bind metal ions and prevent the formation of unwanted deposits. For example, EDTA or citric acid are effective in removing limescale and rust because they form stable complexes with calcium, magnesium, or iron. It is important to select an additive compatible with the main acid – strong mineral acids (e.g., hydrochloric acid) require more robust chelating agents than weak organic acids (e.g., acetic acid).

Another group consists of solubilizers, which increase the solubility of dirt in the cleaning solution. They are particularly used for removing organic contaminants such as fats or oils, which acids alone do not dissolve. Nonionic surfactants with high resistance to acidic environments, such as alkoxylated alcohols, are suitable. When selecting them, it is crucial to verify their stability in an acidic environment – some surfactants may degrade or lose effectiveness at low pH.

Mixing and Homogenization Procedure for Cleaning Agents

Proper mixing is essential for achieving a homogeneous mixture and maximum effectiveness of the cleaning agent. The basic rule is: always add acid to water, never the other way around. This procedure prevents a violent exothermic reaction that could lead to splashing or boiling of the solution. When working with concentrated acids (e.g., 30% hydrochloric acid), it is advisable to cool the mixture to below 25 °C to minimize evaporation and aerosol formation.

After adding the acid, additives are gradually introduced in a precisely defined order. Corrosion inhibitors and stabilizers are usually added first to ensure even distribution in the solution. This is followed by complexing agents and solubilizers, which are mixed at medium speeds (300–500 rpm) for 10–15 minutes. Surfactants are added last to prevent excessive foaming. To achieve optimal homogeneity, it is recommended to use a stirrer with adjustable speeds and monitor the viscosity of the mixture.

Packaging, Storage, and Shelf Life of Acid Cleaners

Proper packaging and storage are crucial for maintaining the effectiveness and safety of acid cleaners. Recommended packaging materials include high-density polyethylene (HDPE) or polypropylene containers, which are acid-resistant and do not allow vapor permeation. Metal containers are unsuitable as they may corrode or react with the contents. Closures must be tight and equipped with safety features such as child-resistant locks or pressure-release valves.

Storage conditions significantly impact the shelf life of the product. The ideal temperature ranges between 10–25 °C, and direct sunlight and freezing must be avoided. High temperatures accelerate the decomposition of additives and surfactants, while low temperatures may cause crystallization or separation of components. The shelf life typically ranges from 6–24 months, depending on the composition and stability of individual components. Before use, it is advisable to check the product’s appearance—cloudiness, sedimentation, or color changes may indicate degradation.

Need a consultation or specific raw materials?

Every application requires an individual approach – whether it’s the choice of acid, corrosion inhibitors, or surfactants. GCG Group provides detailed safety and technical data sheets for every raw material, and our experts will help you with the selection and optimization of formulations for your specific needs. Contact us – or browse our catalog of over 1,300 products.