Sodium metasilicate

Sodium metasilicate (CAS 6834-92-0), also sold under the E-number E550, is an inorganic alkali salt used in industrial cleaning, water treatment, and surface processing.

Where is Sodium metasilicate used?

• Industrial and institutional cleaning: detergent builder
• Heavy-duty formulations: boosts alkalinity, sequesters hardness ions, improves soil removal
• Textile and leather processing: prepares fiber surfaces and controls bath pH
• Scouring and dyeing: improves dye uptake consistency
• Water treatment: corrosion inhibitor for metal pipelines, protecting iron and steel surfaces
• Pulp and paper: stabilizes peroxide bleach in bleaching and sizing, and controls effluent pH
• It forms a protective silicate film on metal surfaces to prevent degradation.
• Used as a starting material for zeolites and silica catalysts.
• Used in water treatment to regulate pH and remove contaminants.
• Used as an ingredient in adhesives.
• Used as a corrosion inhibitor in boiler water feed.

Good to know: The pentahydrate form is the most common. Food-grade material is available under the E550 designation for indirect contact or food-processing applications.

Typical specification

• Pentahydrate is highly soluble in water.
• Has the highest active alkalinity and pH buffering index among inorganic electrolytes.

Regulatory status

• Classified as causing severe skin burns and serious eye damage (H314).
• Classified as possibly irritating to the respiratory tract (H335).
• Anhydrous form has UN number 3253.
• CLP classification is harmonised according to Regulation 1272/2008 (CLP).

Storage, packaging and handling

• Anhydrous form reacts violently with acid and is corrosive to aluminium and zinc, producing flammable/explosive hydrogen gas.
• Anhydrous form is a solid in various forms, colourless to white, hygroscopic.
• Anhydrous form should be stored separately from strong acids, food and feed, metals and halogens.
• Commonly supplied in 25 kg bags.

Frequently asked questions about Sodium metasilicate

Can sodium metasilicate replace other builders in detergent formulations?

It can replace sodium tripolyphosphate in detergents and metal cleaning agents, reducing environmental pollution.

Is sodium metasilicate used in oil well cementing?

It is used in oil well cements to prevent separation of solids from the high water content cement matrix.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.