Chemical Pipe Color Coding Guide

Quick Answer

Under ASME A13.1, chemical pipes carrying toxic or corrosive fluids use white text on an orange background (Pantone 151). BS 1710 uses violet for acids and alkalis and brown for mineral/vegetable/animal oils. Chemical pipe color coding helps workers identify hazardous contents instantly, reducing the risk of accidental exposure during maintenance and emergency response.

Chemical piping systems in refineries, petrochemical plants, and chemical processing facilities carry various hazardous substances including acids, caustics, solvents, and toxic gases. Correct chemical pipe color coding is a fundamental safety requirement.

Chemical Pipe Color Codes by Standard

Chemical Type	ASME A13.1	BS 1710	ISO 14726
Acids (sulfuric, hydrochloric, etc.)	Orange background, white text	Violet	Violet
Caustics (NaOH, KOH)	Orange background, white text	Violet	Violet
Toxic gases (H2S, Cl2, NH3)	Orange background, white text	Yellow with black text	Yellow
Organic solvents	Orange background, white text	Brown	Brown
Mineral oils and fuels	Brown background, white text	Brown	Brown
Oxidizing chemicals	Yellow background, white text	Yellow	Yellow
Corrosive chemicals (general)	Orange background, white text	Violet	Violet

ASME A13.1 Chemical Classification

ASME A13.1 groups chemicals into two hazard categories:

Category	Background	Text	Includes
Toxic and corrosive	Orange (Pantone 151)	White	Acids, caustics, H2S, ammonia, chlorine, corrosive chemicals
Flammable	Brown (Pantone 4515)	White	Hydrocarbons, fuels, organic solvents, flammable gases

The standard does not differentiate between specific chemicals by color. The label text must clearly identify the exact chemical (e.g., “SULFURIC ACID 98%” rather than just “ACID”). This is critical because different chemicals require different emergency response procedures, PPE, and spill containment methods.

Common Chemical Pipe Labels

Chemical	Hazard Category	ASME A13.1 Color	Label Example
Sulfuric acid (H2SO4)	Toxic/corrosive	Orange	”SULFURIC ACID 98%“
Hydrochloric acid (HCl)	Toxic/corrosive	Orange	”HYDROCHLORIC ACID 33%“
Sodium hydroxide (NaOH)	Toxic/corrosive	Orange	”CAUSTIC SODA 50%“
Ammonia (NH3)	Toxic/corrosive	Orange	”ANHYDROUS AMMONIA”
Hydrogen sulfide (H2S)	Toxic/corrosive	Orange	”HYDROGEN SULFIDE”
Methanol (CH3OH)	Flammable	Brown	”METHANOL”
Toluene	Flammable	Brown	”TOLUENE”
Chlorine (Cl2)	Toxic/corrosive	Orange	”CHLORINE GAS”

Pro Tip

For chemical piping, always include the concentration and phase (liquid/gas) on the label text. “Sulfuric acid” could be 10% dilute (moderate hazard) or 98% concentrated (extreme hazard). The color code alone does not convey this critical information. See the full ASME A13.1 reference for label sizing requirements.

Material Compatibility Note

Chemical pipe color coding addresses identification only, not material selection. The pipe material must be compatible with the chemical service. For example, concentrated sulfuric acid can be transported in carbon steel, but dilute sulfuric acid requires alloy materials. Always refer to the piping specification and compatible ASTM materials for chemical service piping.

Read the full guide to pipe color coding