Hydrochloric acid
The strong mineral acid in brick acid and the harshest toilet cleaners. It attacks copper, brass and zinc, and meeting an oxidiser it gives off chlorine gas.
What not to do
CleaningHQ holds 1 recorded hazard for hydrochloric acid. That is everything an authority has been read saying — it is not a list of everything dangerous. A substance missing from it has not been cleared; it has not been established.
Never mix
Chlorine gas is released, and this is the strongest domestic version of the acid-and-bleach reaction because hydrochloric acid is the strongest acid a householder is likely to have. Chlorine causes coughing, chest tightness and shortness of breath, and its effects can be delayed by hours. Get well clear, do not go back in to ventilate, and seek medical advice even if breathing settles.
Hydrochloric acid is unsafe on Anodised aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
- Ventilate the area
Why we say this
Strongly supported
Named acid, named finish.
Sources
AAMA 609 & 610-02: Cleaning and Maintenance Guide for Architecturally Finished Aluminum
American Architectural Manufacturers Association (AAMA), 2002 · Standards body
Relied on for: That cleaners containing hydrochloric acid must not be used on anodised surfaces. (states this directly)
Verification: a person has read the passage relied on.
Read on — Read in full. Sections 3 General, 4.1 light surface soil, 4.3 organic coatings, and 5 Cleaning Precautions. Supports the claim as stated.
Last reviewed by a person on .
Hydrochloric acid is unsafe on Copper and brass
Unsafe
Do not do this. The risk is established, and it is described below.
The reaction releases hydrogen, so this is a fire and explosion warning as well as a damage one.
Precautions
- Ventilate the area
- Wear gloves
- Wear eye protection
Why we say this
Strongly supported
A regulator naming both metals and the gas produced. This is what rules brick acid out anywhere near plumbing fittings and decorative brass.
Sources
Right to Know Hazardous Substance Fact Sheet: Hydrogen Chloride (RTK 1012)
New Jersey Department of Health, 2016 · Government or regulator
Relied on for: That hydrogen chloride will attack many metals such as copper, brass and zinc to release flammable and explosive hydrogen gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'Description and Use' paragraph and the 'Handling and Storage' reactivity list. Supports the claim as stated. Adds the strong mineral acid the catalogue was missing, and supplies a second regulator-sourced route to chlorine gas that does not involve a hypochlorite bottle being poured — the acid side of the same accident.
Last reviewed by a person on .
Hydrochloric acid is unsafe on Stainless steel
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
Why we say this
Strongly supported
The regulator on steel and the steel trade on the specific mechanism for stainless. A chloride-bearing acid is the worst combination for a passive layer.
Sources
Right to Know Hazardous Substance Fact Sheet: Hydrogen Chloride (RTK 1012)
New Jersey Department of Health, 2016 · Government or regulator
Relied on for: That hydrogen chloride corrodes steel. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'Description and Use' paragraph and the 'Handling and Storage' reactivity list. Supports the claim as stated. Adds the strong mineral acid the catalogue was missing, and supplies a second regulator-sourced route to chlorine gas that does not involve a hypochlorite bottle being poured — the acid side of the same accident.
Care and Maintenance of Stainless Steel
British Stainless Steel Association, Stainless Steel Advisory Service, 2001 · Trade or professional body
Relied on for: That chlorides attack the passive layer on stainless steel and cause pitting corrosion. (states this directly)
Verification: a person has read the passage relied on.
Read on — Sprint 29 re-read all four pages: Factors Affecting Maintenance, Maintenance Programme, Cleaning Methods with the whole of Table 1, Table 2, and Notes 1-10. Earlier sprints named both tables but carried only part of one and none of the notes. Supports a wider statement — our claim was widened. SPRINT 29 FOUND THIS UNDER-EXTRACTED WHILE ALL THREE SIGNALS CALLED IT DONE: zero representation debt, in the fully-harvested list, and honestly noted as 'read in full'. Five of Table 1's eleven rows, all of Table 2 and eight of ten notes had never reached the graph. Newly built: tannin and coffee deposits, heat discolouration, the 1% ammonia routine clearance, oxalic acid for embedded iron, and the condition-triggered domestic frequency rule. The paraphrase cap is part of the cause, and the fix is not a longer paraphrase — the facts belong in the citing records.
Last reviewed by a person on .
Hydrochloric acid is unsafe on Polished marble
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
Why we say this
Strongly supported
A manufacturer naming the acid and the stone together, corroborated by the stone trade's general classification. The damage is dissolution of the surface, not a stain on it.
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That limestones and marbles must not be acid cleaned because hydrochloric acid dissolves them. (states this directly)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Care & Cleaning of Natural Stone
Natural Stone Institute · Trade or professional body
Relied on for: That calcareous stone is sensitive to acidic solutions which may dull or etch it. (states this directly)
Verification: a person has read the passage relied on.
Read on — Sprint 29 read all nine sections. Earlier sprints had read three: the siliceous-versus-calcareous classification, cleaning products, and sealing. Supports a wider statement — our claim was widened. Three sections of nine had been read and the source treated as complete. The unread six carry the whole preventive programme - coasters, trivets, non-treated dry mopping, slip-resistant mats, worn vacuum wheels, blot-don't-wipe - none of which the register held. They also answer a priority-1 row reading 'no route answers this yet': the authority's position on etch marks is that they are not a cleaning problem and need professional re-polishing. Two oddities are worth the record: dry 0000 steel wool is permitted on water rings, and efflorescence is removed dry because water makes it worse.
Last reviewed by a person on .
Hydrochloric acid is unsafe on Cement and mortar
Unsafe
Do not do this. The risk is established, and it is described below.
The joint dissolves faster than the deposit does, and joints do not grow back.
Why we say this
Supported
Cement-based materials are carbonate-bearing and are attacked by the same reaction. Recorded as interpretation rather than direct support because the manufacturer's sentence is about stone rather than about mortar, and this catalogue does not put words into it.
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That acid washing is material-dependent and that limestones and marbles are dissolved by hydrochloric acid. (cleaninghq's interpretation of what it says)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Last reviewed by a person on .
Hydrochloric acid is unsafe on Sandstone
Best avoided
The available guidance advises against this.
Precautions
- Test on an inconspicuous area first
Why we say this
Supported
Recorded at avoid rather than unsafe because the manufacturer's own statement is that sandstones VARY. The outcome is a permanent colour change across the slab rather than a localised mark, which is why it is worth a warning even at this strength.
Sources
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That sandstones vary under acid washing and that some turn orange because of their iron content. (states this directly)
Verification: a person has read the passage relied on.
Read on — General Advice, Power Washing, Acid Washing, Seasonal Maintenance, Sealants, the per-stain sections and Organic Growth. Supports the claim as stated.
Last reviewed by a person on .
Hydrochloric acid must never be mixed with Sodium hypochlorite (chlorine bleach)
Unsafe
Do not do this. The risk is established, and it is described below.
The strongest domestic version of the acid-and-bleach reaction, and an outdoor one, where people assume ventilation is not a concern.
Precautions
- Never mix with other cleaning products
- Ventilate the area
- Wear gloves
- Wear eye protection
- Consider professional help
Why we say this
Strongly supported
Paired with a full incompatibility record under /safety, which carries the outcome, the mechanism and what to do after an exposure. The edge exists so the warning reaches both agents' pages without either of them restating it.
Sources
Right to Know Hazardous Substance Fact Sheet: Hydrogen Chloride (RTK 1012)
New Jersey Department of Health, 2016 · Government or regulator
Relied on for: That hydrogen chloride reacts with oxidising agents including chlorine to form toxic chlorine gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'Description and Use' paragraph and the 'Handling and Storage' reactivity list. Supports the claim as stated. Adds the strong mineral acid the catalogue was missing, and supplies a second regulator-sourced route to chlorine gas that does not involve a hypochlorite bottle being poured — the acid side of the same accident.
Dangers of Mixing Bleach with Cleaners
Washington State Department of Health · Government or regulator
Relied on for: That bleach must not be mixed with acidic products because toxic chlorine gas is produced. (states this directly)
Verification: a person has read the passage relied on.
Read on — The whole page: the bleach-and-ammonia section and the bleach-and-acid section. Supports the claim as stated.
Last reviewed by a person on .
Precautions
- Never mix with other cleaning products
- Ventilate the area
- Wear gloves
- Wear eye protection
- Keep away from children and pets
- Rinse thoroughly afterwards
- Consider professional help
In detail
Hydrochloric acid is the strong mineral acid a domestic reader is most likely to encounter, usually under the name brick acid or in the harshest class of toilet-bowl cleaner, and the regulator's own list of uses includes metal pickling and cleaning and, stated plainly, household cleaners. It removes limescale, cement smears and mortar residue faster than any organic acid, and everything that makes it fast makes it dangerous to the surroundings. It corrodes steel, and it attacks many metals — copper, brass and zinc are named — releasing flammable hydrogen gas as it does so. That rules it out anywhere near plated taps, brass fittings, galvanised gutters or a boiler. Two further points decide most real questions about it. Reacting with an oxidising agent it forms chlorine gas, which is the same outcome as the bleach-and-acid accident approached from the acid side. And on any carbonate stone or cement-based grout it does not clean the surface, it dissolves it — the deposit and the substrate are chemically the same target.
Properties
- Chemical name
- Hydrogen chloride solution
- pH
- Strongly acidic
What works
Hydrochloric acid is effective against Limescale Strongly supported
Why
- Hydrochloric acid is explained by pH in cleaning
- Hydrochloric acid is explained by Etching versus staining
- Hydrochloric acid is explained by Corrosion and passivation
Sources for this page
Sources
Right to Know Hazardous Substance Fact Sheet: Hydrogen Chloride (RTK 1012)
New Jersey Department of Health, 2016 · Government or regulator
Relied on for: That hydrogen chloride solution is hydrochloric acid, is used in metal cleaning and household cleaners, attacks copper, brass and zinc releasing hydrogen, corrodes steel, and forms toxic chlorine gas on reaction with oxidising agents. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'Description and Use' paragraph and the 'Handling and Storage' reactivity list. Supports the claim as stated. Adds the strong mineral acid the catalogue was missing, and supplies a second regulator-sourced route to chlorine gas that does not involve a hypochlorite bottle being poured — the acid side of the same accident.
Last reviewed by a person on .