Galvanised steel
Steel protected by a sacrificial zinc layer. Alkaline cleaners dissolve that layer and give off hydrogen doing it, leaving the steel exposed.
What not to do
Potassium hydroxide is unsafe on Galvanised 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
Galvanising is a zinc coating, and consuming the zinc removes the protection rather than cleaning the steel.
Sources
Right to Know Hazardous Substance Fact Sheet: Potassium Hydroxide (RTK 1571)
New Jersey Department of Health, 2010 · Government or regulator
Relied on for: That potassium hydroxide is corrosive in moist air to metals including zinc. (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. Completes the caustic pair, and the aluminium statement is the evidential basis for warning against caustic oven products on aluminium bakeware and trim, which had rested on the sodium hydroxide record alone.
Last reviewed by a person on .
Trisodium phosphate is unsafe on Galvanised steel
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Ventilate the area
Why we say this
Strongly supported
Named metal, named reaction, named gas.
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate solutions react with galvanised iron to produce flammable hydrogen gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'IDENTIFICATION' paragraph and the 'HANDLING AND STORAGE' reactivity list. Supports the claim as stated. Adds the alkaline builder family to the agent records, and gives the catalogue a fourth independent regulator statement that alkalis attack aluminium — which is now sourced from sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium carbonate rather than from one sheet.
Last reviewed by a person on .
Ammonia is unsafe on Galvanised steel
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Ventilate the area
- Wear gloves
Why we say this
Strongly supported
The third metal in the same instruction.
Sources
Right to Know Hazardous Substance Fact Sheet: Ammonium Hydroxide (RTK 0103)
New Jersey Department of Health, 2011 · Government or regulator
Relied on for: That copper, aluminium and galvanised metals must not be used when handling ammonium hydroxide. (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 a wider statement — our claim was widened. Recorded as supporting a wider statement than was claimed. The catalogue warned about ammonia and bleach; this sheet establishes that ammonia solution also has a metals problem, which reaches brass taps, copper pans, aluminium window frames and galvanised outdoor fittings — none of which the existing record covered.
Last reviewed by a person on .
Acetic acid (vinegar) is unsafe on Galvanised steel
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Ventilate the area
Why we say this
Supported
The same statement applied to a zinc coating, whose whole function is to be consumed in preference to the steel beneath. Recorded at supported rather than strongly supported because the sheet names metals generally rather than zinc specifically.
Sources
Right to Know Hazardous Substance Fact Sheet: Acetic Acid (RTK 0004)
New Jersey Department of Health, 2016 · Government or regulator
Relied on for: That acetic acid attacks many metals forming flammable and explosive hydrogen gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'Description and Use' block and the 'Handling and Storage' reactivity list. Supports a wider statement — our claim was widened. Recorded as supporting a wider statement than was claimed. The catalogue warned that vinegar etches carbonate stone and damages seals; this establishes a metals reaction with a flammable product, and an incompatibility with acetone, neither of which the record carried.
Last reviewed by a person on .
In detail
Galvanising coats steel with zinc, which corrodes in preference to the steel underneath — a sacrificial protection that works only for as long as the zinc lasts. Anything that consumes the zinc faster than weather would is therefore shortening the life of the component rather than cleaning it, and alkalis are the main culprit. A state health department's fact sheets record it plainly from three directions: trisodium phosphate in water solution reacts with aluminium, zinc and galvanised iron to produce flammable hydrogen gas; potassium hydroxide is corrosive in moist air to zinc among other metals, again forming hydrogen; and ammonium hydroxide carries an explicit instruction not to use copper, aluminium or galvanised metals when handling it. That rules out caustic degreasers, sugar-soap products, ammonia-based cleaners and oven cleaner on galvanised gutters, sheds, dustbins, watering cans and fencing. Acids attack the zinc too, so the workable range is narrow: a neutral detergent, a soft brush and a rinse. White powdery deposits on galvanised metal are zinc corrosion products rather than dirt, and scrubbing them off removes more of the coating than leaving them alone would.
Properties
Sensitivity
- Acids
- Recorded
- Alkalis
- Recorded
- Chlorine bleach
- Not known
- Abrasion
- Recorded
- Porous
- Not applicable
“Not known” means CleaningHQ has not established this, not that the material is unaffected.
Why
- Galvanised steel is explained by Sacrificial protection
- Galvanised steel is explained by Alkali attack on light metals
- Galvanised steel is explained by Corrosion and passivation
Related
- Galvanised steel is commonly affected by Algae
- Galvanised steel is commonly affected by Rust
- Galvanised steel is commonly affected by Moss and lichen
Hacks and claims involving this
Sources for this page
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate in water solution reacts with aluminium, zinc and galvanised iron to produce flammable hydrogen gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'IDENTIFICATION' paragraph and the 'HANDLING AND STORAGE' reactivity list. Supports the claim as stated. Adds the alkaline builder family to the agent records, and gives the catalogue a fourth independent regulator statement that alkalis attack aluminium — which is now sourced from sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium carbonate rather than from one sheet.
Right to Know Hazardous Substance Fact Sheet: Ammonium Hydroxide (RTK 0103)
New Jersey Department of Health, 2011 · Government or regulator
Relied on for: That copper, aluminium and galvanised metals must not be used when handling ammonium hydroxide. (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 a wider statement — our claim was widened. Recorded as supporting a wider statement than was claimed. The catalogue warned about ammonia and bleach; this sheet establishes that ammonia solution also has a metals problem, which reaches brass taps, copper pans, aluminium window frames and galvanised outdoor fittings — none of which the existing record covered.
Last reviewed by a person on .