If you are searching for a practical, versatile, and industrial-grade cleaning and surface preparation solution in manageable quantities, Phosphoric Acid 20% is one of the most useful chemicals available to individual customers in the UK.

Whether you are restoring tools, preparing metal for painting, etching concrete, removing rust, descaling equipment, or cleaning masonry, a 20% phosphoric acid solution offers an excellent balance between strength and control.

At HD Chemicals LTD, we supply Phosphoric Acid 20% in UN-approved fluorinated safety bottles, available in:

• 500ml

• 1 Litre

• 2 Litres (2 x 1L bottles)

You can purchase directly from our store here:
👉 where to buy phosphoric acid 20% UK online

Visit our main chemical supplier homepage:
👉 https://shop.hdchemicals.co.uk/

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What Is Phosphoric Acid 20%?

Phosphoric acid (H₃PO₄) is a mineral acid widely used in industrial cleaning, surface treatment, rust conversion, and descaling processes.

A 20% solution means:

• 20 grams of pure phosphoric acid per 100 grams of solution

• Or approximately 200 grams per litre (depending on density)

This concentration is strong enough for effective industrial cleaning, yet diluted enough to allow safe handling with appropriate PPE.

Unlike stronger 85% industrial concentrates, the 20% solution:

• Is easier to control

• Requires less dilution

• Is more suitable for small workshops and DIY users

• Reduces risk during handling

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Why 20% Concentration Is Ideal for Individual UK Users

Many industrial suppliers sell 75–85% phosphoric acid in large containers (5L, 25L, 200L drums). For most individual customers, this is:

• Excessively strong

• More hazardous

• Difficult to store safely

• Not cost-effective for small jobs

Phosphoric Acid 20% is ideal because:

This makes HD Chemicals’ packaging sizes perfectly matched for UK customers.

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Industrial & DIY Applications of Phosphoric Acid 20%

Below is a complete breakdown of practical, non-food industrial uses.

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1. Rust Removal and Rust Conversion

How Phosphoric Acid Removes Rust

Rust is iron oxide (Fe₂O₃). When phosphoric acid reacts with iron oxide, it converts it into iron phosphate, which:

• Is black in colour

• Is stable

• Forms a protective layer

• Improves paint adhesion

Chemical Reaction (Simplified)

Iron oxide + phosphoric acid → iron phosphate + water

This conversion process is what makes phosphoric acid superior to vinegar or citric acid for serious rust removal.

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Example 1: Cleaning Rusty Garden Tools

Materials Needed:

• 100 ml Phosphoric Acid 20%

• Plastic tray

• Gloves and eye protection

• Nylon brush

Steps:

1. Pour 100 ml into a plastic tray.

2. Submerge rusty metal parts.

3. Leave for 30–90 minutes.

4. Scrub lightly.

5. Rinse with water.

6. Dry thoroughly.

For heavier corrosion, you may require 200–300 ml.

A

500ml bottle can restore approximately 10–15 medium garden tools.

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Example 2: Car Chassis Restoration

For a small car chassis section (approx. 1 m²):

• Apply 250–500 ml using brush or spray.

• Leave 1–3 hours.

• Wipe and neutralise.

• Prime after drying.

One 1L bottle can treat approximately 2–4 m² of moderate rust.

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2. Metal Surface Preparation Before Painting

Phosphoric acid is widely used in industry before:

• Powder coating

• Spray painting

• Primer application

• Anti-corrosion treatment

It creates a micro-etched surface that improves mechanical adhesion.

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Dilution for Surface Prep

For light surface preparation:

• Mix 500 ml acid + 500 ml clean water

• Final strength: approx. 10%

Application rate:

• 100–150 ml per m²

So 1 litre diluted solution covers approx. 6–10 m².

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3. Concrete Etching and Floor Preparation

Before applying epoxy paint or sealants, concrete must be etched.

Phosphoric acid reacts with calcium carbonate in concrete, opening pores and removing laitance.

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Example: Etching a 20 m² Garage Floor

Estimated usage:

• 50–100 ml per m²

• Total needed: 1–2 litres (depending on porosity)

Dilution ratio:

• 1 part acid : 1 part water for moderate etching

• Always add acid to water, never reverse.

Procedure:

1. Sweep floor.

2. Pre-wet surface.

3. Apply diluted acid evenly.

4. Scrub with stiff brush.

5. Leave 10–15 minutes.

6. Rinse thoroughly.

7. Neutralise with baking soda solution.

Two 1L bottles (2L option) are ideal for full garage preparation.

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4. Descaling Boilers and Heating Elements

Limescale (calcium carbonate) reduces efficiency in:

• Immersion heaters

• Industrial kettles

• Pipework

• Closed-loop systems

Phosphoric acid dissolves scale without excessive aggression like hydrochloric acid.

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Example: Cleaning a 10L Water Tank

Dilution:

• 200 ml phosphoric acid 20%

• 800 ml water

Fill tank and leave for 1–3 hours.

Rinse thoroughly.

A 500ml bottle can descale multiple small systems.

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5. Brickwork and Masonry Cleaning

Common UK issues:

• Efflorescence

• Cement haze

• Lime staining

• Mortar smears

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Example: Cleaning 10 m² Brick Wall

Dilution:

• 1 part acid : 3 parts water

Application:

• 50–80 ml per m²

Total needed: approx. 500–800 ml diluted solution.

A 1L bottle is sufficient for most residential projects.

 

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6. Laboratory and Workshop Cleaning

Phosphoric acid is effective for:

• Removing metal residues

• Cleaning glassware (industrial use)

• Degreasing metal surfaces

• Removing oxide films

Usage example:

• 100 ml diluted solution for cleaning multiple components.

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Safe Storage and Handling in the UK

HD Chemicals LTD supplies Phosphoric Acid 20% in:

• UN-approved

• Fluorinated HDPE bottles

• Chemical-resistant packaging

• Secure caps

Why this matters:

• Prevents chemical permeation

• Minimises vapour release

• Safe for domestic workshop storage

• Compliant with UK transport standards

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Storage Guidelines

• Store between 5°C–25°C

• Keep upright

• Avoid metal shelving

• Keep away from alkalis

• Keep out of reach of children

Shelf life: typically 24+ months when sealed.

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How Much Should You Buy?

For most UK homeowners, the 1L option offers best balance of value and versatility.

Purchase safely here:
👉 where to buy phosphoric acid 20% UK online

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Why Buy from HD Chemicals LTD?

✔ UK-based supplier
✔ Small quantity options
✔ UN-approved fluorinated packaging
✔ Secure shipping
✔ Industrial-grade quality
✔ Designed for individual customers

Main store:
👉 https://shop.hdchemicals.co.uk/

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Frequently Asked Questions (FAQs)

1. Is 20% phosphoric acid strong enough for rust removal?

Yes, it effectively converts rust without being excessively aggressive.

2. Can I dilute it further?

Yes. You can dilute 1:1 or 1:3 depending on the task.

3. How much do I need for 10 m² concrete?

Approximately 500 ml to 1 litre depending on surface condition.

4. Is it safer than hydrochloric acid?

Yes. It is less aggressive and produces fewer fumes.

5. Can I store it in my garage?

Yes, in its original UN-approved bottle.

6. Does it damage paint?

Yes, it can. Avoid contact with finished surfaces.

7. How long does it last unopened?

Typically 2+ years if stored correctly.

8. Can I use it on stainless steel?

With caution. Test first on small area.

9. Is PPE required?

Yes. Gloves and eye protection minimum.

10. Is this suitable for home users?

Yes, when used responsibly with safety precautions.

Technical Specification – Phosphoric Acid 20% (Aqueous Solution)

Below is a detailed technical specification suitable for product pages, safety documentation, workshop reference, and commercial customer enquiries for Phosphoric Acid 20% Solution supplied by HD Chemicals LTD.

This specification is aligned with typical industrial-grade 20% phosphoric acid solutions used for rust removal, descaling, surface preparation, masonry cleaning, and metal treatment applications (non-food industrial use).

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1. Product Identification

Product Name: Phosphoric Acid 20% Solution
Chemical Name: Orthophosphoric Acid (Aqueous Solution)
Chemical Formula (active component): H₃PO₄
CAS Number: 7664-38-2
EC Number: 231-633-2
UN Number: UN 1805
Transport Class: 8 (Corrosive)
Packing Group: III (for diluted solution such as 20%)

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2. Composition / Information on Ingredients

Concentration Type: Weight/weight (w/w)

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3. Physical and Chemical Properties

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4. Chemical Characteristics

• Moderate-strength inorganic acid

• Triprotic acid (three dissociable hydrogen ions)

• Reacts with:

  • Iron oxides (rust conversion)

  • Calcium carbonate (scale removal)

  • Alkalis (neutralisation reaction)

  • Reactive metals (hydrogen evolution possible)

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5. Typical Industrial Applications (Non-Food)

• Rust conversion

• Metal surface preparation

• Concrete etching

• Limescale removal

• Descaling heating systems

• Brick and masonry cleaning

• Equipment maintenance

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6. Packaging Information (HD Chemicals LTD)

Container Type:

• UN-approved

• Fluorinated HDPE bottles

• Chemical-resistant caps

• Tamper-evident seal

Available Sizes:

• 500 ml

• 1 Litre

• 2 Litres (2 × 1L)

Fluorinated bottles significantly reduce vapour permeation compared to standard HDPE containers.

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7. Storage Requirements

• Store at 5°C to 25°C

• Keep container tightly closed

• Store upright

• Avoid direct sunlight

• Keep away from:

  • Alkalis

  • Reactive metals

  • Strong oxidising agents

Shelf Life: 24+ months in original sealed container.

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8. Hazard Classification (Typical CLP Classification for 20%)

Hazard Class:

• Skin Irrit. 2

• Eye Dam. 1

Hazard Statements:

• H315: Causes skin irritation

• H318: Causes serious eye damage

Signal Word: Danger

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9. Personal Protective Equipment (PPE)

When handling:

• Chemical-resistant gloves (nitrile recommended)

• Safety goggles or face shield

• Protective clothing

• Adequate ventilation

For industrial spraying applications:

• Respiratory protection if mist is generated

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10. Handling Guidelines

• Always add acid to water when diluting.

• Never mix with chlorine-based products.

• Avoid contact with aluminium or zinc unless controlled.

• Neutralise spills with sodium bicarbonate before cleaning.

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11. Dilution Guidance for Industrial Applications

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12. Transport Information

• UN 1805

• Class 8 – Corrosive

• Packing Group III (diluted solution)

• Not environmentally classified as hazardous for transport in small quantities

• Supplied in compliant UN-rated packaging