When an aluminium extruder sets up a pre-anodising brightening bath, when a carbonated-beverage line gives its drink that familiar tang, and when an industrial cleaning formulator dissolves a stubborn lime-and-rust stain, the same molecule is at work: phosphoric acid. Known in chemistry as orthophosphoric acid (H3PO4), this medium-strength mineral acid unites industries as far apart as metal finishing and food production around a single raw material. This guide covers the chemical identity of phosphoric acid, its 75-85% concentration grades, the difference between technical and food grade (E338), its uses by industry, and the packaging, safety and documentation issues that decide a B2B purchase — in Turkey and for export.
What Is Phosphoric Acid?
Phosphoric acid is a triprotic mineral acid with the chemical formula H3PO4, meaning it ionises in water in three stages, releasing protons step by step. In its pure state it is a colourless, odourless crystalline solid (melting point ~42 °C), but in commerce it is almost always bought and sold as a clear, colourless, slightly viscous aqueous solution. Compared with hydrochloric or sulphuric acid it is a medium-strength acid: the first ionisation step is pronounced, while the second and third are weak. In practice this behaviour is highly valuable — it delivers controlled acidity and buffering without aggressively attacking surfaces.
This "moderate" character is precisely why phosphoric acid is so widespread across both the food and metalworking worlds. The same molecule can give a beverage a refreshing sourness at low concentration and build a protective phosphate layer on a steel surface at high concentration.
Identity and key data
| Property | Value / description |
|---|---|
| Chemical name | Orthophosphoric acid (phosphoric acid) |
| CAS number | 7664-38-2 |
| EC number | 231-633-2 |
| Molecular formula | H3PO4 |
| Molar mass | 97.99 g/mol |
| Food additive code | E338 |
| Appearance | Colourless, clear, viscous liquid (solution) |
| Odour | Odourless |
| Commercial concentrations | 75%, 80%, 85% (by weight) |
| Acid character | Medium-strength, triprotic |
| ADR class | Class 8 (corrosive), UN 1805 |
Industrial phosphoric acid is produced mainly by two routes. The wet process dissolves phosphate rock with sulphuric acid; it is the main source for fertiliser and technical applications and carries higher impurity levels. The thermal / purified process produces acid by burning and hydrating yellow phosphorus, or by purifying wet-process acid, and is the source for food and high-purity applications. This difference in origin directly determines which grade you should buy.
Concentration Grades and the Technical vs. Food Grade Difference
Two parameters must be clarified when buying phosphoric acid: concentration and grade.
On the concentration side, the most common commercial form is the 85% solution; this is close to the highest stable concentration of H3PO4 practically achievable in water and offers the "not shipping water" advantage in freight. The 75% and 80% forms are also preferred for easier-to-pump viscosity, especially in automatic dosing systems. As concentration rises the solution becomes noticeably more viscous; 85% acid approaches the consistency of honey in the cold, and heating may be needed for pumping in winter months.
The grade side becomes critical when food applications are involved:
- Technical grade: for industrial uses such as metal treatment, detergents, water treatment and fertiliser. Usually of wet-process origin; its fluoride, sulphate and heavy-metal content may not be suitable for food.
- Food grade (E338): pure enough to be used as a beverage and food acidulant. Heavy metals such as arsenic, lead and cadmium, as well as fluoride, are limited according to food-codex specifications (e.g. FCC / E338).
The most common purchasing mistake is using technical grade in a food application for a price advantage, or conversely, buying needlessly expensive food grade for a simple metal-cleaning job. The correct grade must be chosen clearly, based on whether the process is food-contact or not.
| Grade | Typical concentration | Key impurity criterion | Typical use |
|---|---|---|---|
| Technical grade | 75-85% | General industrial limits | Phosphating, detergents, water treatment |
| Technical (low iron) | 75-85% | Low Fe, low colour | Aluminium brightening, metal finishing |
| Food grade (E338) | 75-85% | Heavy metal + fluoride limited (FCC) | Beverages, food acidulant, yeast nutrient |
| Pharmaceutical / USP | 85% | Strictest impurity limits | Pharma, laboratory, special applications |
When ordering, confirming the concentration both as a percentage and together with the requested grade avoids the confusion that arises from different suppliers' naming conventions. For every batch, Yüksek Kimya shipments include a certificate of analysis (COA) showing concentration, grade and impurity values.
The Main Uses of Phosphoric Acid
The strength of phosphoric acid lies in its versatility: it dissolves metal oxides and forms a protective phosphate layer, gives food controlled sourness and buffering, strips limescale and rust stains, and is the direct raw material for phosphate-based compounds.
Metal surface treatment: phosphating and rust conversion
The most characteristic industrial use of phosphoric acid is metal surface preparation. Two core functions stand out:
- Phosphating: forms a thin, porous iron/zinc phosphate layer on the steel surface. This layer provides both a first barrier against corrosion and significantly improves the adhesion of paint, powder coating or electrostatic coating. It is a standard pre-paint step on automotive body lines, white-goods panels and furniture profiles.
- Rust converter: phosphoric acid converts red iron oxide (Fe2O3, i.e. rust) into a more stable, inert iron phosphate. This is a practical solution that "stops" rust on surfaces that cannot be fully cleaned and prepares the ground for paint.
In the aluminium sector, phosphoric acid is the main component of chemical and electrolytic brightening baths, giving profiles and decorative aluminium surfaces a bright, smooth finish. Because the amount of iron passing into the bath affects surface quality, a low-iron technical grade is preferred for these applications.
Food and beverage industry: acidulant E338
Food grade phosphoric acid appears in food legislation under the code E338 as an acidity regulator. Its best-known use is in cola and carbonated beverages; it gives the drink its characteristic sharp sourness and lowers the pH to around 2.5, supporting both taste and microbiological stability. Compared with citric acid it offers a "sharper / more mineral" sourness profile at a lower cost.
Other food applications include use as a phosphorus source / nutrient salt in yeast production and fermentation, acidity regulation in some cheese and sugar-refining processes, and as an intermediate for producing food phosphate salts (e.g. sodium and calcium phosphates). Only E338 food grade should be used in these applications.
Detergents and industrial cleaning: lime and rust remover
In cleaning-chemical formulations, phosphoric acid is a powerful lime and rust remover. It dissolves limescale from calcium and magnesium carbonate, lifts rust and oxide stains from metal surfaces, and lightly passivates the surface. Because it damages metal surfaces less than aggressive products containing hydrochloric acid and carries no chlorine-gas risk, it stands out as a safe alternative, especially on stainless steel and aluminium surfaces.
Typical applications:
- Acidic cycles of CIP (cleaning-in-place) in dairy, food and beverage plants
- Descaling in industrial kitchens and steam boilers
- Bathroom / sanitary cleaner and rust-stain remover formulations
- Acidic cleaning before surface passivation
For detail on the components and formulation logic of detergent and industrial cleaning chemicals, see our guide to cleaning and detergent chemicals.
Water treatment and industrial process
In water treatment, phosphoric acid and its derivative phosphates are used as corrosion and scale inhibitors in boiler and cooling-water systems, forming a protective film on the metal surface that extends the life of pipes and equipment. Controlled phosphate dosing is also applied in drinking-water networks to reduce the release of lead and copper (only within the appropriate grade and regulatory framework).
Fertiliser and agriculture
Globally, the largest consumption area for phosphoric acid is the fertiliser industry. Wet-process phosphoric acid is the main raw material for phosphate fertilisers such as DAP (diammonium phosphate), MAP (monoammonium phosphate) and superphosphate. It also appears in liquid-fertiliser formulations for drip-irrigation systems, acting both as a phosphorus source for the plant and as a line cleaner that dissolves the limescale clogging the drippers.
Choosing the Right Grade by Industry
The same product is bought with different grade and concentration expectations across different industries. The table below summarises which grade makes sense in which application:
| Industry | Typical application | Preferred grade / concentration |
|---|---|---|
| Automotive & metalworking | Phosphating, pre-paint prep | Technical 75-85% |
| Aluminium profile | Chemical / electrolytic brightening | Technical, low-iron 85% |
| Beverage production | Acidulant (cola, carbonated drinks) | Food grade E338 75-85% |
| Detergent / cleaning | Lime-rust remover, CIP acid | Technical 75-85% |
| Water treatment | Corrosion / scale inhibition | Technical / appropriate grade |
| Agriculture-fertiliser | Phosphate fertiliser, liquid fertiliser | Technical / fertiliser grade |
A practical dilution example
For plants that dilute on site, a simple mass calculation is enough. Suppose you want to prepare 1,000 kg of a 20% solution:
- Pure H3PO4 required: 1,000 × 0.20 = 200 kg
- An 85% product contains 0.85 kg H3PO4 per kg: 200 / 0.85 ≈ 235 kg of 85% acid
- Make-up water: 1,000 − 235 = 765 kg water
During dilution the acid must always be added slowly and with stirring into the water, never the reverse. This calculation also shows why buying bulk 85% is more economical than buying ready-diluted product in most scenarios: every extra tonne of water shipped comes back as freight cost.
Safety: GHS Classification and Corrosive-Material Management
Although phosphoric acid is a medium-strength acid, it is classified as a corrosive substance under GHS. The label carries the GHS05 (corrosion) pictogram and the signal word "Danger". Typical hazard statements:
- H290: May be corrosive to metals
- H314: Causes severe skin burns and eye damage
- H302 (in relevant cases at high concentrations): assessed per the relevant specification
The basic rules for working safely on site:
- PPE: acid-resistant gloves (nitrile/neoprene), closed goggles or face shield, acid apron; full face protection for transfers with splash risk.
- Dilution direction: always add acid to water, never the reverse; the process is exothermic.
- Incompatible materials: on contact with carbon steel, galvanised metal and aluminium, phosphoric acid corrodes the metal and can release flammable hydrogen gas. Contact with strong bases causes violent exothermic neutralisation.
- Eye wash and safety shower: must be within 10 seconds' reach of filling and transfer points.
For detailed information on reading labels, pictograms and how to interpret H/P statements, see our GHS and CLP labelling guide. Phosphoric acid is less volatile than hydrochloric acid and carries no chlorine-gas risk; to compare corrosive-acid management in a broader frame, our hydrochloric acid guide is a complementary resource.
Packaging and Storage: Jerrycan, Drum, IBC and Tanker
The most critical supply feature of phosphoric acid is that, being corrosive, it cannot be carried in metal packaging. All packaging, piping, pumps and storage equipment must be made of acid-resistant material: HDPE, PP, PVC, GRP (FRP) or 316 stainless steel. Carbon steel and aluminium must be strictly avoided.
| Packaging | Typical capacity | Material | Suitable user profile |
|---|---|---|---|
| Plastic jerrycan | 30-35 kg | HDPE | Low consumption, trial orders |
| Drum | 250-330 kg | HDPE | Medium consumption, laboratory/workshop |
| IBC tote | 1,000 L (~1,400-1,450 kg) | HDPE body + steel cage | Regular consumption, forklift-equipped sites |
| Tanker (bulk) | 20-25 tonnes | Rubber-lined / PE / 316 stainless | Phosphating lines, high tonnage |
Note: because the density of 85% phosphoric acid is ~1.68-1.69 g/cm³, a 1,000 L IBC carries roughly 1,400-1,450 kg of product; this matters when ordering, to avoid confusing the litre and kilogram equivalents.
The same rule applies on the storage side: fixed tanks should be HDPE, PP, GRP or 316 stainless, and there must be a containment bund (secondary containment) around the tank at least equal to the tank volume. Because 85% acid becomes viscous in the cold and can partially crystallise around ~21 °C, heat tracing / trace heating on tanks and pipelines is necessary at most plants. Crystallisation does not spoil the quality; once heated and stirred, the product returns to normal.
ADR Class 8 Transport: UN 1805
Phosphoric acid solutions are carried by road under ADR Class 8 (corrosive substances), with the number UN 1805 (usually packing group III). In practice this requires:
- An ADR-certified driver and suitable vehicle
- UN-certified packaging (UN code on jerrycans, drums and IBCs)
- Orange plate and Class 8 hazard label
- Written instructions in the vehicle (transport emergency card) and an appropriate PPE set
Making the shipment ADR-compliant is not only a legal obligation but also an element that safeguards the buyer's liability during insurance and occupational-safety audits. For export orders the same corrosive-goods logic applies under IMDG (sea) and IATA (air), and Incoterms should be agreed in advance. Yüksek Kimya carries out corrosive-product shipments with ADR-compliant logistics.
Quality Documents: SDS, COA and Specification Check
In a corporate purchase, the document set that comes with the product is as important as the price:
- SDS (Safety Data Sheet): hazard, first-aid, storage and disposal information in the 16-section format. Your plant's risk assessment and emergency plan rely on this document.
- COA (Certificate of Analysis): batch-specific H3PO4 content (%), density, iron (Fe, ppm), chloride, sulphate and fluoride values; for food grade, additionally the heavy-metal limits (As, Pb, Cd).
- Specification compliance: process-specific criteria such as a low-iron limit for metal brightening or E338 heavy-metal limits for food applications must be confirmed in writing before ordering.
For food grade phosphoric acid, the parameters typically monitored include H3PO4 content (min. 75% or 85%), heavy metals (total and individual ppm), fluoride (max. ppm) and colour/clarity. Confirming the correct grade with documentation is indispensable for audit compliance, especially in food and beverage production.
Factors Affecting the Price of Phosphoric Acid
Five variables are decisive when you ask about the price of phosphoric acid:
- Grade: food grade (E338) and purified product are priced higher than technical grade; the cost of purification is reflected in the price.
- Concentration: there is a difference in both unit price and transport efficiency between 75%, 80% and 85%; 85% carries less "water".
- Volume and continuity: regular monthly IBC or tanker purchases offer a clear per-unit advantage over one-off jerrycan/drum orders.
- Packaging type: bulk tanker gives the lowest unit cost; with drums and jerrycans the packaging cost is reflected in the price.
- Market balance: because phosphoric acid supply is tied to phosphate-rock and sulphuric-acid production, fluctuations in those markets flow through to the price.
For a sound comparison, request quotes from the supplier with identical grade, concentration, packaging, delivery terms and document set.
Phosphoric Acid Supply from Yüksek Kimya
Yüksek Kimya is a B2B chemical supplier providing wholesale phosphoric acid from its facility in Kestel, Bursa, across Turkey — Marmara above all — and for export. Alongside phosphoric acid, our acids category includes complementary products such as hydrochloric, nitric, sulphuric and acetic acid; for product detail and technical specifications, see our phosphoric acid product page within the acids category.
The principles our supply process rests on:
- Certified quality: ISO 9001, ISO 14001, ISO 45001 and GHP certified operation; SDS and COA shared with every shipment
- Technical and food grade options: technical or E338 food grade product to match your application
- Flexible packaging: 30-35 kg jerrycan, drum, 1,000 L IBC and tanker options
- ADR-compliant shipping: certified transport for Class 8 corrosive products
- Fast quotes: same-day pricing by phone or via the contact form
To request a quote: state the grade you need (technical or food/E338), the concentration (75%, 80% or 85%), your estimated monthly tonnage and your preferred packaging, and reach us via our contact page; our sales team will share the right grade for your application and the current phosphoric acid price with you the same day. The same channel supports trial orders and sample requests.
Related reading
Frequently Asked Questions
Is phosphoric acid the same as orthophosphoric acid?
Yes. In everyday commerce the two names refer to the same product. Orthophosphoric acid (H3PO4) is the most stable and most common form of phosphoric acid, and when the market simply says phosphoric acid it almost always means an aqueous solution of this compound. Its CAS number is 7664-38-2 and commercial solutions are usually sold between 75% and 85% by weight.
What is the difference between food grade and technical grade phosphoric acid?
Both contain the same molecule, but the purity and impurity limits differ. Food grade phosphoric acid (E338) meets food-codex limits for impurities such as heavy metals (arsenic, lead, cadmium), fluoride and sulphate, and can be used as a beverage acidulant. Technical grade is intended for industrial uses such as metal phosphating, detergents and water treatment, and must not be used in food-contact processes.
How is phosphoric acid packaged and shipped?
Because phosphoric acid is corrosive it ships only in acid-resistant plastics: 30-35 kg HDPE jerrycans, roughly 250-330 kg drums, 1,000 L IBC totes (about 1,400-1,450 kg net) and road tankers for high tonnage. Storage and transfer equipment should be HDPE, PP, PVC or 316 stainless steel; carbon steel and aluminium must be avoided.
What determines the price of phosphoric acid?
Price is driven by grade (technical or food/E338), concentration (75%, 80% or 85%), order volume, packaging type (jerrycan, drum, IBC, tanker), delivery distance and the current phosphate-rock market. The most reliable way to compare quotes is to state the exact grade, concentration and monthly tonnage you need and request a written offer on identical terms.