Which chemical is used for tank cleaning?

The most common chemicals used for tank cleaning are alkaline degreasers, acidic descalers, and solvent-based cleaners. The right choice depends on the type of residue left inside the tank. For hydrocarbon-based residues such as crude oil or fuel, alkaline degreasers are typically the first line of defence. For mineral scale or rust, acidic agents are more effective.

Tank cleaning is rarely a one-size-fits-all operation. The combination of residue type, tank material, regulatory environment, and required surface condition all influence which cleaning approach delivers the best result. This article walks through the key questions maintenance engineers and field technicians face when selecting and applying tank cleaning solutions.

What types of residue determine which chemical to use?

The type of residue inside a tank is the primary factor in selecting a cleaning chemical. Hydrocarbon residues such as crude oil, diesel, and lubricants respond best to alkaline or solvent-based cleaners. Inorganic deposits such as limescale, rust, and mineral buildup require acidic descalers. Biological growth and microbial contamination call for biocidal or oxidising agents.

Understanding the residue composition before selecting a cleaning agent prevents wasted effort, unnecessary chemical exposure, and potential damage to the tank lining. Here is a practical breakdown:

• Hydrocarbons (crude oil, fuel, lubricants): Alkaline degreasers or aromatic solvents break down the carbon chains and emulsify the oil for easier removal.
• Mineral scale and rust: Acidic cleaners such as phosphoric or citric acid dissolve inorganic deposits without aggressive mechanical action.
• Wax and paraffin: High-temperature water combined with solvent-based agents is typically required, as wax does not dissolve easily in water alone.
• Biological and microbial residues: Oxidising biocides or quaternary ammonium compounds target bacteria and biofilm that accumulate in water or food-grade tanks.
• Coatings and paint residues: These generally require mechanical removal or high-pressure water jetting rather than chemical treatment alone.

In many industrial facilities, tanks contain a mixture of residues, which means a sequenced cleaning approach is often necessary: a degreasing stage followed by an acid wash, for example, or a solvent flush before a final water rinse.

What are the most common chemicals used in tank cleaning?

The most common chemicals used in industrial tank cleaning solutions are alkaline degreasers, acidic descalers, solvents, and oxidising agents. Each class of chemical targets a specific type of contamination and is selected based on residue type, tank material compatibility, and the required cleanliness standard after the job.

Alkaline degreasers

Alkaline cleaners are among the most widely used tank cleaning solutions in petrochemical and industrial settings. They work by saponifying fats and emulsifying oils, making them highly effective against hydrocarbon residues. Sodium hydroxide (caustic soda) and potassium hydroxide are common active ingredients. These agents are often diluted in hot water to increase their effectiveness and speed up the cleaning process.

Acidic descalers

Acidic agents such as phosphoric acid, hydrochloric acid, and citric acid are used to dissolve mineral scale, rust, and calcium deposits. They are particularly common in water storage tanks, heat exchangers, and process vessels where hard water scale builds up over time. Concentration levels must be carefully controlled to avoid damaging metal surfaces or tank coatings.

Solvents

Solvent-based cleaners are used when residues are not water-soluble, such as waxes, bitumen, or heavy oils. They are effective but require careful handling due to flammability and vapour toxicity risks. In many facilities, solvent use is being reduced in favour of hot water or high-pressure mechanical methods for environmental and safety reasons.

Oxidising agents

Hydrogen peroxide and sodium hypochlorite are used in tanks where biological contamination is a concern, such as water treatment tanks, food processing vessels, and ballast water tanks on ships. These agents break down organic matter and kill microbial colonies effectively.

How do chemical cleaning agents actually work inside a tank?

Chemical cleaning agents work by reacting with the target residue at a molecular level, breaking down the bonds that hold it to the tank surface. Alkaline agents saponify and emulsify oils, acidic agents dissolve mineral bonds, and oxidising agents break apart organic molecules. The effectiveness of any chemical depends on concentration, temperature, contact time, and agitation.

In practice, chemical cleaning inside a tank follows a defined sequence. The agent is introduced into the tank, either by spraying, flooding, or circulation. It then dwells on the surface for a set period to allow the chemical reaction to occur. Mechanical agitation, whether from spray nozzles, circulation pumps, or jetting equipment, accelerates the process by continuously exposing fresh chemical to the surface.

Temperature plays a significant role. Many alkaline degreasers perform considerably better at elevated temperatures because heat increases the reaction rate and reduces the viscosity of oily residues, allowing the chemical to penetrate more effectively. Acidic descalers also benefit from moderate heat, though excessive temperatures can accelerate corrosion of the tank itself.

Once the dwell time is complete, the spent chemical and loosened residue are flushed out, typically with water. Depending on the application, a neutralising rinse may follow to bring the tank surface to a safe pH before it is returned to service or prepared for coating.

What are the safety risks of using chemicals for tank cleaning?

The primary safety risks of using chemicals for tank cleaning include toxic vapour exposure, chemical burns, fire and explosion hazards from solvents, and confined space dangers. These risks are compounded when working inside enclosed vessels where ventilation is limited and escape routes are restricted. Proper risk assessment, personal protective equipment, and adherence to industry safety standards are essential.

Operators working with tank cleaning chemicals should be trained in line with standards set by recognised safety organisations. In Europe, the EWJI (European WaterJet Industry) provides guidance on safe practices in industrial cleaning environments. In the Netherlands, SIR sets the framework for certified training. In the UK, the WJA (WaterJet Association) and, in the USA, the WJTA (WaterJet Technology Association) both publish safety guidelines relevant to industrial cleaning operations. In Germany, DIRV covers safety requirements for industrial cleaning professionals.

Key safety measures when working with tank cleaning chemicals include:

• Confined space entry procedures: Tanks must be assessed for oxygen levels, toxic gas concentrations, and flammable vapours before entry is permitted.
• Personal protective equipment: Chemical-resistant suits, gloves, face shields, and respiratory protection are required depending on the agent being used.
• Ventilation: Forced ventilation is essential when working with solvents or any chemical that produces toxic or flammable vapours.
• Chemical compatibility checks: The cleaning agent must be verified as compatible with the tank material and any residual product to avoid dangerous reactions.
• Waste disposal: Spent chemical and contaminated rinse water must be handled and disposed of in accordance with local environmental regulations.

When is high-pressure water jetting a better alternative to chemical cleaning?

High-pressure water jetting is a better alternative to chemical cleaning when the residue is primarily physical rather than chemically bonded, when chemical use poses unacceptable environmental or safety risks, or when the required surface condition demands mechanical removal rather than dissolution. It is also preferred when tanks need to be returned to service quickly, since there is no dwell time, neutralisation, or chemical waste disposal involved.

Water jetting operates across a wide pressure range, typically from 500 bar “7,250 PSI” up to 3,000 bar “43,500 PSI”, making it highly adaptable. At lower pressures, it is effective for rinsing and light cleaning. At ultra-high pressures above 2,000 bar “29,000 PSI”, it can remove hardened coatings, rust, and even concrete without the use of any chemical agents.

In petrochemical and energy facilities, high-pressure water jetting is often the preferred tank cleaning solution for the following reasons:

• No chemical residue remains on the surface, which is critical when tanks are to be recoated or inspected.
• The process is faster for large surface areas, especially when robotic systems are deployed.
• It eliminates the risk of chemical reactions with tank contents or materials.
• It reduces the volume of hazardous waste generated compared to chemical cleaning.
• Closed-circuit systems can collect water and debris simultaneously, keeping the work area clean and dry.

Can chemicals and high-pressure water jetting be used together?

Yes, chemicals and high-pressure water jetting can be used together and frequently are in demanding industrial cleaning applications. Chemical agents are used to break down or loosen residue, and high-pressure water jetting then removes it mechanically. This combined approach is often faster and more thorough than either method used alone, particularly when dealing with thick hydrocarbon deposits or heavily scaled surfaces.

A common sequence in oil storage tank cleaning, for example, involves an initial chemical degreasing stage to emulsify and soften the oil sludge, followed by high-pressure water jetting to physically strip the loosened material from the tank walls and floor. The mechanical action of the water jet also ensures the chemical agent reaches fresh surface layers, improving overall effectiveness.

When combining both methods, sequencing and compatibility are critical. The chemical must be fully rinsed before a high-pressure rinse is applied at pressures that could force residual chemical into cracks or weld seams. Similarly, if the jetting follows a solvent treatment, adequate drying or purging time may be required before high-pressure water is introduced, particularly in confined spaces where flammable vapour could still be present.

How MagTrack Supports Tank Cleaning Operations

When tank cleaning requires mechanical precision, minimal human exposure, and a consistently clean, dry surface, robotic high-pressure water jetting offers a significant advantage over manual or purely chemical approaches. Our MagTrack robotic crawler system is built specifically for these demands.

MagTrack is a modular magnetic crawler system designed for flat and slightly curved steel surfaces, operating with high-pressure water tools up to 3,000 bar “43,500 PSI”. It is directly applicable to oil storage tank cleaning, cargo hold cleaning, and surface preparation ahead of coating. Key advantages for tank cleaning operations include:

• Closed-circuit waterblasting: The Blast Can vacuum dome collects water and debris simultaneously, leaving a clean, dry surface without leakage, which is essential when preparing a tank for inspection or recoating.
• Curved surface capability: The Curved Blast Can variant handles surfaces with a radius of up to 3 meters “approximately 10 feet”, making it suitable for smaller storage tanks and vessel hulls.
• Reduced human exposure: Remote-controlled operation keeps operators away from confined spaces and high-pressure zones, directly addressing the safety risks associated with tank cleaning.
• ATEX Zone 2 availability: The MagTrack Mini is available as a certified ATEX unit, making it suitable for use in potentially explosive atmospheres such as petrochemical storage tanks.
• Modular tooling: Depending on the residue and surface condition, different tool attachments can be fitted to the same carrier, allowing the system to adapt to the specific demands of each tank cleaning job.

Whether you are evaluating robotic tank cleaning solutions for a new project or looking to reduce chemical use in your maintenance programme, we are ready to help. Contact our team to discuss your specific requirements and find out how MagTrack can be configured for your application.