| Water transfer and general-purpose service | Aluminum | Lightweight and commonly used for water-discharge hose connections. | Convenient where reducing handling weight matters; may corrode in some wet or salty environments. | Check the water chemistry, exposure to salt, pressure rating, and compatibility with the mating connection. |
| Fuel, oils, and general non-corrosive liquids | Brass | Often used for fluid connections and offers good corrosion resistance in many ordinary service conditions. | Suitable for many indoor and outdoor applications, but not for every chemical or atmosphere. | Confirm compatibility with the exact fluid and any additives. Avoid assuming brass is suitable for ammonia or strong acids. |
| Corrosive liquids or demanding washdown service | 316 stainless steel | Provides broad corrosion resistance and is commonly selected for more demanding environments. | Useful in many humid or chemical-exposure settings; chloride-rich conditions can still cause pitting or crevice corrosion. | Verify chemical concentration, temperature, chloride exposure, and the coupler’s pressure rating. |
| Less corrosive industrial or utility service | 304 stainless steel | Offers corrosion resistance for many general applications and is typically considered where 316 is not required. | May be unsuitable for prolonged exposure to high-chloride or highly corrosive environments. | Compare the expected exposure with the manufacturer’s material-compatibility data. |
| Many acids, alkalis, and other compatible chemicals | Polypropylene | Can resist a range of chemicals and does not rust. | May be a practical choice in corrosive settings, but can be more vulnerable to impact, heat, and mechanical stress than metal. | Check chemical compatibility at the actual concentration and temperature, plus pressure, UV exposure, and connection design. |
| Heavy-duty water, slurry, or industrial discharge | Ductile iron | Provides a strong, robust option for applications where mechanical durability is important. | Heavier than aluminum or plastics; exposed or damaged surfaces may corrode, especially in wet environments. | Check lining or coating suitability, abrasion conditions, operating pressure, and the weight supported by the hose assembly. |
| Non-corrosive service where strength and cost are key factors | Carbon steel | Can provide a durable metal connection for suitable industrial applications. | Unprotected steel can rust when exposed to moisture or corrosive atmospheres. | Confirm coating or lining compatibility with the fluid, and inspect for corrosion or coating damage during service. |