Maintaining a clean hull is essential for performance, efficiency, and long-term vessel protection. While many boat owners focus on antifouling, staining above the waterline — including rust streaks, tannin marks, and yellow discolouration — is just as important.

One of the most effective professional-grade treatments available is Oxalic Acid Solution 9.95%, widely used across UK marinas and marine yards for restoring fibreglass hulls to their original brightness.

If you are searching for where to buy Oxalic Acid Solution 9.95% in the UK online, you can order directly from our specialist supplier here:

👉 Buy Oxalic Acid Solution 9.95% for Marine Hull Cleaning – UK Delivery Available
https://shop.hdchemicals.co.uk/products/oxalic-acid-5-solution

You can also browse our complete chemical range here:
👉 HD Chemicals – Trusted UK Chemical Supplier
https://shop.hdchemicals.co.uk/

Why Hull Staining Requires a Chemical Solution

Boat hull staining is rarely removed effectively with detergents alone. Most stains are chemical in nature, meaning they require a chemical reaction to break them down.

Common causes include:

• Iron oxide deposits from marina water

• Run-off from stainless fittings

• Tannin staining in freshwater moorings

• Oxidised organic residue

• Mineral scum at the waterline

These stains embed into gelcoat pores, making mechanical scrubbing ineffective and potentially damaging.

Oxalic acid works by chemically dissolving and chelating these contaminants rather than abrading them away.

What Is Oxalic Acid? (Technical Overview)

Oxalic acid is an organic dicarboxylic acid with the chemical formula:

C₂H₂O₄

It is the simplest dicarboxylic acid and contains two carboxyl (-COOH) functional groups. This structure gives it strong chelating properties — meaning it forms stable complexes with metal ions, particularly iron (Fe³⁺).

Key Chemical Properties of Oxalic Acid

Understanding the 9.95% Concentration

A 9.95% solution means:

• 9.95 grams of oxalic acid per 100 grams of total solution

• Approximately 99.5 grams per litre

So if you use:

• 5 litres of solution → roughly 497.5 grams of active oxalic acid

This concentration is strong enough to dissolve iron oxide efficiently while still being manageable for safe manual application.

How Oxalic Acid Reacts with Rust (Iron Oxide)

Rust is primarily iron(III) oxide (Fe₂O₃).

Oxalic acid reacts with iron oxide to form soluble iron oxalate complexes:

Fe₂O₃ + 6H₂C₂O₄ → 2Fe(C₂O₄)₃³⁻ + 3H₂O + 6H⁺

This reaction converts insoluble rust into a water-soluble compound that can be rinsed away.

This is why oxalic acid removes rust staining without heavy scrubbing.

Chelation Mechanism

Chelation occurs when oxalic acid binds to metal ions using its two carboxyl groups. The molecule effectively “grabs” iron ions and keeps them dissolved in water.

This makes oxalic acid particularly effective for:

• Rust streaks

• Waterline iron deposits

• Metal contamination marks

Why Oxalic Acid Is Ideal for Fibreglass Gelcoat

Fibreglass gelcoat is porous at a microscopic level. Organic stains and iron deposits settle into these micro-pores.

Oxalic acid:

• Penetrates surface contamination

• Lifts staining chemically

• Does not mechanically abrade gelcoat

• Minimises surface thinning

This preserves the integrity of the hull.

Application Guide for Boat Hull Cleaning

Equipment Required

• Oxalic Acid Solution 9.95%

• Plastic bucket

• Measuring jug (litres/millilitres)

• Soft sponge or brush

• PPE (gloves, eye protection)

• Fresh water supply

Dilution Guidance

Heavy staining:

• Use neat (undiluted 9.95%)

Moderate staining:

• Mix 1 litre solution with 0.5 litres water

Light maintenance cleaning:

• Mix 1 litre solution with 1 litre water

Application Steps

1. Pre-rinse hull thoroughly.

2. Apply solution evenly to damp surface.

3. Leave for 5–20 minutes.

4. Rinse thoroughly with fresh water.

5. Repeat if required.

Usage Examples in Litres & Active Grams

Example 1 – 6 Metre Boat

Waterline only:

• 2.5 litres used

• ≈ 248.75 grams active oxalic acid

Example 2 – 8 Metre Cruiser

Full hull:

• 7 litres used

• ≈ 696.5 grams active ingredient

Example 3 – 10 Metre Yacht

Heavy seasonal staining:

• 10 litres used

• ≈ 995 grams active ingredient

Safety Data Considerations

Although effective, oxalic acid must be handled responsibly.

Hazard Classification (Typical)

• Irritant

• Harmful if swallowed

• Causes serious eye irritation

Always Use

• Chemical-resistant gloves

• Protective eyewear

• Adequate ventilation

Avoid mixing with:

• Chlorine-based products

• Strong alkalis

Environmental Considerations

Oxalic acid is biodegradable and breaks down into carbon dioxide and water under environmental conditions.

However:

• Avoid direct discharge into natural waterways

• Use controlled yard drainage systems

• Rinse responsibly

Storage & Stability

• Store between 5°C and 25°C

• Keep tightly sealed

• Avoid direct sunlight

• Keep away from oxidising agents

Shelf life: typically 12+ months when stored correctly.

When to Use Oxalic Acid on Your Boat

Best times include:

• Before seasonal launch

• At haul-out

• Before resale

• After freshwater mooring

• When visible staining appears

Regular maintenance prevents long-term gelcoat oxidation.

Why Buy from HD Chemicals?

We supply:

• Reliable 9.95% concentration

• Fast UK dispatch

• Competitive pricing

• Bulk options for marine professionals

• Consistent quality

If you're looking for where to buy Oxalic Acid Solution 9.95% in the UK online, order directly here:

👉 Order Oxalic Acid Solution 9.95% – UK Marine Cleaning Grade
https://shop.hdchemicals.co.uk/products/oxalic-acid-5-solution

Explore our full chemical range:
👉 https://shop.hdchemicals.co.uk/

Frequently Asked Questions (FAQs)

1. Is Oxalic Acid 9.95% safe for gelcoat?

Yes, when used as directed and rinsed thoroughly.

2. How does it remove rust?

It chemically converts iron oxide into soluble iron oxalate.

3. Can it damage antifouling paint?

Avoid applying directly to antifouling coatings.

4. What PPE is required?

Gloves and eye protection minimum.

5. Can I dilute it further?

Yes, for light maintenance cleaning.

6. Is it biodegradable?

Yes, but must still be used responsibly.

7. How much do I need for a 7m boat?

Approximately 4–8 litres depending on staining.

8. Can professionals spray apply it?

Yes, with appropriate safety controls.

9. How long does it last in storage?

Typically 12 months or more when stored properly.

10. Where can I buy Oxalic Acid Solution 9.95% in the UK?

Order directly from our UK supplier here:
👉 https://shop.hdchemicals.co.uk/products/oxalic-acid-5-solution