Buyer’s Guide · Hydrochloric Acid

Hydrochloric Acid Grades Explained: 30% vs 33% vs 35% — Which One Should You Buy?

If you’ve ever gotten two hydrochloric acid quotes with different percentages and wondered which one is actually right for your job, you’re not alone. This guide breaks it down in plain language — no chemistry degree required — so you can write an RFQ that gets you the correct grade on the first try.

Hydrochloric acid (HCl) is one of the most-traded industrial acids in the world, and also one of the most mislabelled. Buyers ask for “concentrated HCl,” “muriatic acid,” “20 Baumé,” or a straight percentage — and often mean four slightly different things. Get the concentration wrong and you either overpay for acid you don’t need, or under-order for a job that needs more punch. This guide covers what 30%, 32%, 33% and 35% w/w actually mean, which one fits which job, and how to specify it correctly so your supplier — and your Certificate of Analysis — match what you actually ordered.

The short answer: for almost every industrial buyer — steel pickling, mining, water treatment, general cleaning — 30–33% w/w commercial-grade HCl is the right default. It’s the most stable strength to ship and store, it’s what most of the industry means by “muriatic acid,” and you dilute it down to your actual working strength anyway. Only reach for 35% if you specifically need more active acid per drum and can handle the extra fumes that come with it. SNJ Exim supplies 33% w/w as our standard export specification for exactly this reason.

First, Some Clarity

What Do Hydrochloric acid grades “30%,” “33%” and “20° Baumé” Actually Mean?

Three terms, one number — here’s how they connect.

When someone says “muriatic acid,” they usually mean commercial-grade HCl somewhere between 28% and 35% strength — most often around 31–33%. When a chemist says “concentrated HCl,” they usually mean something closer to 35–37%, the practical ceiling before the acid starts losing HCl gas to the air faster than it’s useful. And when an older spec sheet says “20° Baumé,” that’s an old-fashioned density scale that happens to equal about 31.5% w/w — while “22° Baumé” is closer to 35%.

This mix of labels is exactly why RFQs go wrong. A buyer asks for “20 Baumé” expecting 35% strength, gets 31.5%, and assumes the supplier shorted them. Nobody shorted anybody — they were just using two different rulers. The fix is simple: always specify % w/w on your purchase order, and treat Baumé or “concentrated” as a secondary description, not the actual spec.

Side-by-Side

30% vs 32% vs 33% vs 35% Compared

The physical differences that actually matter for buyers and plant safety teams.

Parameter	30% w/w	32% w/w	33% w/w (SNJ Exim standard)	35% w/w
Approx. Baumé	~19°	~20°	~20.5°	~22°
Specific gravity	~1.15	~1.16	~1.16	~1.17–1.18
Fuming when opened	Mild	Moderate	Moderate	Strong, visible fumes
Common trade name	Commercial / muriatic	Muriatic, 20°Bé	Commercial concentrated	22°Bé / near-concentrated
Best suited for	General pH control, textiles	Water treatment, food-grade lots	Mining, pickling feed, general export	Oilfield, high-demand pickling

Values shown are typical, standard-reference figures. Always confirm the exact specific gravity and concentration against the lot Certificate of Analysis.

A Point Most Buyers Miss

The Acid You Buy Isn’t the Acid You Use

Almost every application dilutes the purchased acid before it touches the process.

This is the single most useful thing to understand before you place an order: nobody pours 33% acid straight onto steel or into a water tank. It gets diluted first. Steel pickling baths typically run at 8–18% strength. Boiler descaling uses roughly 5–10%. Concrete and efflorescence cleaning is diluted anywhere from 1:3 to 1:10 with water. Even oil-well acidizing, which uses some of the strongest working concentrations, usually sits around 15%, not 33% or 35%.

That means your real decision isn’t “what strength do I need for my process” — it’s “what strength gets me the most active acid per container, so I’m not paying to ship water.” That’s exactly why 33% is the sweet spot for export: it’s strong enough to minimise freight cost per tonne of active HCl, but not so strong that it fumes aggressively in transit or storage.

By Industry

Which Grade Fits Your Application?

A quick-reference rundown of where HCl gets used, and what concentration to specify.

Mining & Ore Leaching

Base-metal and gold leaching typically runs 8–20% working strength. Buy 33% commercial grade and dilute on site — this is our highest-demand HCl application among mining buyers in South Africa and the wider Southern Africa belt.

Steel Pickling & Galvanizing

Pickling baths run 8–18%. Concentrated acid straight from the drum would fume too aggressively for plant conditions — 33% technical grade, diluted on arrival, is the standard feedstock.

Oil-Well Acidizing

Carbonate acidizing typically uses around 15% HCl, occasionally up to 28% for tougher formations. GCC oilfield buyers blend high-strength commercial acid with inhibitors on location — relevant for buyers across the UAE and GCC.

Water & Effluent Treatment

pH correction and ion-exchange resin regeneration typically use 5–10% HCl — a common need for municipal and industrial water plants across Kenya and Nigeria. Many plants also pair HCl with sodium hypochlorite for full water treatment coverage.

Textile & RMG Processing

Used for desizing and neutralising residual alkali after bleaching. Many Bangladesh RMG dye houses use commercial 33% grade for this step, though acetic acid is often preferred for final neutralisation because it’s gentler on effluent.

Construction & Concrete Cleaning

Efflorescence removal and concrete etching use heavily diluted acid — roughly 1:3 for heavy staining, 1:10 for general cleaning. No need to buy anything stronger than 30–33%.

The Indian Standard

IS 265: The Spec Behind Every Indian-Origin HCl Shipment

If your supplier is Indian, this is the standard your COA is measured against.

Indian Standard IS 265:2021 sets out five grades of hydrochloric acid, and the difference between them mostly comes down to one thing: how much iron is allowed. More iron means a cheaper, more industrial-purpose acid; less iron means a cleaner, more expensive acid suited to food or lab use.

Grade	Min. Acidity	Max. Iron (Fe)	Typical Use
Technical	30.0%	≤ 50 ppm	Pickling, mining, general industrial (SNJ Exim standard export grade)
Boiler Water	30.0%	≤ 20 ppm	Boiler feedwater plants
Food Grade	30.0%	≤ 10 ppm	Corn syrup, gelatin, food pH adjustment
Chemical Pure (CP)	32.0%	≤ 1 ppm	Fine chemical manufacture
Analytical Reagent (AR)	32.0%	≤ 0.4 ppm	Laboratory and analytical work

Practical takeaway: if you’re sourcing for pickling, mining, water treatment or general industry, Technical grade at 33% w/w — our standard export specification — covers you. Only step up to Food Grade if your process actually touches food, beverage or pharmaceutical products.

Worth Knowing Before You Order

Higher Strength Means More Fumes, Not Just More Acid

A safety consideration that should factor into your purchasing decision.

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Fuming Rises Sharply Above 33%

HCl vapour release increases much faster than the concentration itself — 35% fumes noticeably more than 30–33%.

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Corrosion to Nearby Structures

Stronger fumes attack metal roofing, wiring and sprinkler systems faster — a real cost for enclosed plants.

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More Ventilation, More PPE

All HCl grades need gloves, goggles and ventilation — but 35% demands more rigorous fume control and may need acid-gas respirators.

Bottom line: unless your process specifically needs the extra strength, 30–33% delivers everything most buyers need with meaningfully less fume, corrosion and PPE burden than 35%.

Avoid These

5 Mistakes Buyers Make When Specifying HCl

Small wording problems on an RFQ that lead to big mismatches on delivery.

Mixing Up Baumé and % w/w

20° Baumé is about 31.5% w/w; 22° Baumé is about 35%. State the percentage — treat Baumé as a secondary reference only.

Assuming “Muriatic” = “Concentrated”

Commercial muriatic acid (~31–34%) and lab-grade concentrated HCl (~37%) are not the same product. Confirm the actual percentage on the SDS.

Ordering Buying-Strength Instead of Working-Strength

Your process might run at 10%, but you should still buy 33% and dilute — paying to ship diluted acid wastes money on freight.

Assuming Higher % Is Always Better

35% costs more to handle safely. For most jobs, 30–33% is the more economical delivered choice once fume control is factored in.

Ignoring the Iron Limit

Technical grade (≤50 ppm Fe) is fine for pickling and mining. Food, pharma or sensitive textile work needs Food Grade or better — check before you order.

Buyer FAQ

Common Questions

What’s the difference between 30%, 33% and 35% hydrochloric acid?▾

Mainly strength and fuming behaviour. 30–33% is the standard commercial/industrial concentration used for pickling, mining and water treatment. 35% carries more active acid per litre but fumes noticeably more and needs stricter ventilation. Most buyers are better served by 30–33%.

Is 33% hydrochloric acid the same as muriatic acid?▾

Yes, in trade terms “muriatic acid” usually refers to commercial-grade HCl in the 28–35% range, and 33% sits comfortably inside that range. It’s the same product, just a different name commonly used in industrial and construction contexts.

What concentration of HCl does SNJ Exim export?▾

Our standard export specification is 33% w/w Technical grade under IS 265, with iron at or below 50 ppm. Low-iron and food-grade specifications are available on request, confirmed on each lot’s Certificate of Analysis.

Do I need food-grade HCl for my process?▾

Only if your process directly touches food, beverage or pharmaceutical products — for example, corn syrup manufacture, gelatin production or pH adjustment in food processing. For pickling, mining, general industry and water treatment, Technical grade is the correct and more economical choice.

Why not just buy the highest concentration available?▾

Higher concentration means more fuming, faster corrosion of nearby equipment, and stricter PPE and ventilation requirements. Since almost every application dilutes the acid before use anyway, 30–33% usually delivers the best balance of cost, safety and performance.

How should I word my RFQ to get the right grade?▾

State the concentration as a percentage w/w (e.g. “33% min”), reference the grade against IS 265 (Technical, Food, etc.), and state your maximum acceptable iron content in ppm. Also mention your end use so your supplier can flag if a different grade fits better.