Chemical laboratory

Phosphoric Acid

Industrial-Grade Acid for Rust Removal & Metal Treatment

  • CAS 7664-38-2
  • Formula H₃PO₄
  • Flash Pt N/A °C
  • Density 1.685 g/cm³ (for 85% solution)
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Physical & Chemical Properties

Property Value Unit
Boiling point 158°C (for 85% solution) °C
Flash point N/A °C
Density 1.685 g/cm³ (for 85% solution) g/cm³
Solubility Miscible with water -
Ph < 1 (concentrated) -
Molecular weight 98.00 g/mol g/mol
Melting point 42.35°C °C
Vapor pressure 0.03 mmHg at 20°C mmHg
Autoignition temp N/A -
Appearance Clear, colorless liquid -
Odor Odorless -
Vapor density 3.4 (air = 1) g/cm³

Overview

Phosphoric acid (H₃PO₄) is a versatile inorganic acid that serves as an essential chemical in numerous industrial and commercial applications. This clear, colorless liquid with a molecular weight of 98.00 g/mol is highly soluble in water and maintains excellent stability under normal conditions. With its strong acidic properties (pH < 1 when concentrated), phosphoric acid is particularly renowned for its effectiveness in metal treatment, rust removal, and surface preparation applications.

Key Applications

Phosphoric acid excels in rust removal and metal surface treatment, where it chemically converts iron oxide (rust) into water-soluble iron phosphate compounds that can be easily removed. This makes it invaluable for automotive restoration, metal fabrication, and maintenance operations. In fertilizer production, phosphoric acid serves as a critical raw material for manufacturing phosphate fertilizers that provide essential nutrients for agricultural crops. The chemical also functions as an effective pH adjustment agent in water treatment systems, industrial processes, and pool maintenance, offering precise control over acidity levels. Additionally, phosphoric acid serves as an etching agent for metal surfaces, preparing them for coating applications, welding, or further processing by removing oxides and creating optimal surface conditions.

Safety & Handling

Phosphoric acid is non-flammable with no flash point or autoignition temperature, making it safer to handle than many organic solvents. However, proper safety protocols are essential due to its corrosive nature. Always wear appropriate personal protective equipment including chemical-resistant gloves, safety goggles, and protective clothing when handling this acid. Ensure adequate ventilation in work areas to prevent vapor accumulation, and have emergency eyewash stations and safety showers readily available. Never add water directly to concentrated acid; always add acid to water slowly while stirring to prevent violent reactions and heat generation.

Storage & Shelf Life

Store phosphoric acid in corrosion-resistant containers such as polyethylene, polypropylene, or specially lined steel tanks. Maintain storage temperatures between 10-30°C to prevent crystallization or degradation. Keep containers tightly sealed and away from incompatible materials including strong bases, metals (particularly iron and aluminum), and oxidizing agents. When stored properly, phosphoric acid maintains its quality indefinitely, though periodic testing is recommended for critical applications. Ensure storage areas have appropriate containment systems and ventilation to handle potential spills or vapor emissions.

Why Alliance Chemical

Alliance Chemical provides reliable supply of high-quality Phosphoric Acid The Ultimate Rust Remover Solution with same-day shipping from our Taylor, Texas facility. We offer flexible shipping options including UPS for smaller quantities and LTL/FTL freight for bulk orders. Every shipment includes comprehensive Safety Data Sheets (SDS) and Certificates of Analysis (COA) to ensure product quality and regulatory compliance. Our technical support team is available to assist with application questions and proper handling procedures.

Shipping & Availability

Parcel Shipping

UPS Ground supports pints, quarts, and most 1-gallon packages nationwide.

LTL Freight

5-gallon pails, drums, and totes move via LTL carriers such as ABF Freight, SEFL, Saia, and XPO.

Full Truckload

FTL available for palletized bulk orders. Competitive freight rates.

Local Pickup

Will-call pickup available at our Taylor, TX warehouse for Texas customers.

SDS, COA, and TDS available for every product • Most orders ship in 1-2 business days from Taylor, TX

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Frequently Asked Questions

What is phosphoric acid (H3PO4) and what is it used for?
Phosphoric acid (CAS 7664-38-2, formula H3PO4) is a clear, inorganic acid commonly used as a rust remover, descaler and reagent in industrial and laboratory settings. Typical uses include metal surface preparation, cleaning and rust conversion, phosphate treatments and general acidification in non-food industrial processes.
How should I store 30% phosphoric acid and what is its shelf life?
Store in a cool, dry, well-ventilated area away from incompatible materials (alkalis, metals) in tightly closed corrosion-resistant containers at 5–30°C with secondary containment. When kept sealed and under recommended conditions, shelf life is typically 12–24 months; verify stability with the supplier’s Certificate of Analysis (COA).
What personal protective equipment and precautions are required when handling phosphoric acid?
Use chemical-resistant gloves (nitrile/NEOPRENE), eye protection or face shield, acid-resistant apron and work in a fume-ventilated area or use local exhaust. In case of contact, flush exposed areas with water and remove contaminated clothing, and seek medical attention for significant exposures; follow the product SDS for detailed first-aid and emergency measures.
What is the difference between 30% phosphoric acid and higher concentrations?
A 30% solution is a moderate-strength formulation well suited for rust removal, lab reagents and many industrial cleaning tasks, offering lower vapor pressure and handling risk versus concentrated grades. Higher concentrations (e.g., technical 75–85%) are used in fertilizer manufacture and chemical synthesis and present increased corrosivity and stricter transport/handling controls.
What documentation is available for phosphoric acid (SDS, COA, TDS)?
Suppliers typically provide a Safety Data Sheet (SDS), Certificate of Analysis (COA) showing assay and impurities, and a Technical Data Sheet (TDS) with typical physical properties and recommended uses. Additional documents such as transport declarations and product-specific risk assessments can be supplied on request.
How is phosphoric acid shipped and what packaging options are common?
Phosphoric acid is classified as a corrosive material (UN 1805, Class 8) and is shipped under applicable hazardous materials regulations; packaging and documentation vary by mode and jurisdiction. Common packaging includes HDPE drums (25–250 kg), IBCs (≈1000 L), and sealed bottles for lab quantities, with tamper-evident and corrosion-resistant inner liners.
Which materials are compatible or incompatible with phosphoric acid?
Phosphoric acid is compatible with many plastics (HDPE, PP, PTFE), glass and certain alloys such as stainless steels (304/316) and nickel-based materials; long-term compatibility depends on concentration and temperature. Avoid use with aluminum, zinc, copper and their alloys, as those materials can corrode or generate hazardous hydrogen gas on contact.
What are the typical technical specifications for 30% phosphoric acid?
Typical specifications for a 30% w/w grade include assay ~30% H3PO4, appearance clear to slightly viscous colorless liquid, density approximately 1.17–1.19 g/cm³ at 20°C, and pH typically <2; exact values vary by batch. For definitive limits and analytical results, consult the product COA or TDS supplied by the manufacturer.
Which industries and applications commonly use phosphoric acid as a rust remover?
Industries using phosphoric acid include metal fabrication, automotive maintenance, surface treatment and laboratories for rust removal, descaling, metal cleaning and phosphate conversion coatings. It is also used in industrial processes requiring controlled acidification and as a reagent in analytical and research labs.
How can I purchase 30% phosphoric acid and what are typical lead times and minimum orders?
30% phosphoric acid is available from chemical distributors in lab bottles to bulk IBCs and drums; minimum order quantities and lead times vary by supplier and location. Contact a certified supplier for current pricing, sample availability, custom packaging, regulatory documentation and estimated lead times (often days to a few weeks depending on stock and logistics).

Documentation & Downloads

Safety Data Sheet
SDS / MSDS
Request COA
Certificate of Analysis
Technical Data Sheet (TDS)
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