Stainless steel and copper are generally both ideal for indoor and outdoor applications and both hold up well over time. In fact, there are more similarities than differences between these two metals. In saying that, which one is right for your project?
There are different types of piping systems used in industries today, the most common ones being process piping and service piping. Process piping is responsible for transporting fluids between processing units and storage tanks within an industrial facility. On the other hand, service piping carries water, air, steam and other fluids for processing.
Some of the piping materials that have been used in industrial applications include:
Increasingly, stainless steel and copper are used in industrial piping projects. Therefore, a study of the two metals is imperative to help understand their individual features and application preferences.
These two selections have unique functional properties and features that make them preferred metals for industrial piping and other applications.
Copper piping is usually made from pure or almost pure copper which is available in both drawn and annealed forms. The plain ends to copper tubing are normally joined by brazing, soldering and with flanged and flared fittings. Press fit is also an option, without hot works or specialised labour.
Stainless steel, on the other hand, comprises of a variety of alloys with chromium content ranging from 12 to 30 per cent, which protects it as long as the localised concentration is in excess of 12 per cent. Despite sharing some attributes, stainless steel and copper have lots of dissimilarities worth looking at.
To read more about stainless steel chromium content and corrosion resistance click here.
Corrosion resistance is the ability of piping systems to remain unaffected by the corrosive effects of the fluids flowing through it as well as any external corrosive forces. The corrosion can be general, localised or both.
Stainless steel pipes can withstand corrosion, thanks to the passive chromium oxide layer that forms on the surface. It performs particularly well against chloride-induced stress corrosion.
Copper pipes, on the other hand, corrode easily when exposed to gases such as carbon dioxide, sulphur dioxide, and hydrogen sulfide. Exposure to acidic environments can cause corrosion in the internal copper piping. In water pipes, this can cause water discolouration and copper poisoning.
The fluid flow rate in piping is usually affected by many factors such as pipe dimension and roughness. Comparing steel and copper piping head to head shows that the roughness in copper pipes slows down the flow of water and other fluids.
Comparatively, stainless steel pipes allow for higher flow rates without running the risk of structural corrosion and piping failure.
Stainless steel is on average 2.5 times stronger than copper and performs far much better on the strain and stress tests. The relatively weaker structure for copper makes its piping vulnerable to external forces that may cause cracks and leaks.
With the above being said, copper is a much softer and malleable metal. This means it can be bent easily into various shapes thereby reducing the need for fasteners and additional fixtures during piping.
Also, the rigidity and lightness of copper tubes make them ideal for long run installations. However, a cost-benefit analysis must be considered during planning as copper pricing tends to fluctuate more than their stainless-steel counterparts.
Steel is a good conductor of heat and electricity. However, copper is an excellent conductor of both heat and electrical energy hence its common usage in heat exchangers.
Stainless steel and copper have varied mechanical and chemical properties. Because of this, their applications in industrial piping also differ, though, in other areas they are used interchangeably.
Water piping: Stainless steel pipes can carry both cold and hot water.
Oil and gas piping: There is great demand for stainless steel in this industry. Especially offshore oil, where greater pressure is put on stainless steel pipes installed in harsh corrosive environments.
Condensation lines: Resistance to corrosion and the inherent capacity of stainless steel to handle high temperature and pressure makes it a perfect fit for condensation lines.
Wastewater piping: Stainless steel is strong, corrosive resistant, and maintains pressure during its operation. These properties ensure successful wastewater conveyance.
Piping for fire sprinkler systems: Steel piping has noncorrosive, hydraulic, and cost advantages. Therefore, it has become one of the commonly used piping materials for both retrofits and new build projects.
Food and beverage pipes: Stainless steel is a safe material that can be used to transport food and drinkable liquids without the risk of contamination.
Heat exchanger tubing: The amazingly higher heat transfer coefficients of copper piping makes it possible to produce cost-effective, and resource-efficient heat exchangers for the HVAC industry.
Water distribution systems: The high tensile strength of copper makes it possible to have thin piping walls and still withstand the pressure of the water flowing through. Pipes can also be bent with ease into different shapes as desired.
Medical gas and vacuum suction pipelines: Here, copper is cleaned and degreased, and the tubes joined firmly using capillary fittings.
Electrical components and power generators: The electrical conductivity of copper easily lends it to integration in electrical components.
Motor vehicle radiators: The thermal conductivity of copper makes it a go-to material for vehicle radiators.
Drain, waste, and vent (DMV) systems: Seamless copper tubes are acceptable by most plumbing codes and therefore popular for DMV installations.
As long as the installation work is done professionally, both stainless steel and copper can last long enough without major maintenance requirements. However, copper may need to be checked for discolouration and localised leaks after some time. Steel is far much easier to install and this cuts down on labour cost and time. This is certainly more true when installed in press fit, where welding is not necessary.
Click here to learn more about press fit tube installation.
Very often, one of the main factors of environmental impact of metals are directly related to its longevity. The other is its recyclability.
Both metals can be and are commonly recycled. Stainless steel being one of the most recycled materials (more than paper or glass), and copper can retain performance even after recycling process.
To have a clear understanding of both metals, it is important to look at their upsides and downsides.
Durability: Stainless steel is more durable than copper and can withstand harsh conditions.
Appearance: Maintains consistent colour throughout lifetime of product.
Lightweight: Making it easy to install
High corrosion resistance: Also highly resistant to rusting.
Tensile strength: Recognised as a premium metal for high end applications.
Minimal maintenance: Applications known to last for decades.
Easy to mold: Being a more malleable metal, it is easier to bend and mold to fit different applications.
Fire resistant: Able to withstand extreme heat.
Almost impossible to rust: Great for domestic applications where users don’t need to worry about rusting issues.
Thermal conductivity: Copper has the highest thermal conductivity of any engineering material, hence its common use in heat exchangers.
Unique aesthetics: Depending on the aesthetic taste, the natural discolouration of copper gives it a unique look to the metal, suitable for applications needing a vintage appeal.
High costs: Applications can come with a high upfront cost. However, this applies to all quality products and can be seen as an investment rather than a cost.
Difficult to bend: Due to its tensile strength, it is harder to bend than copper.
Possibility of water spotting: Depending on the application it is possible to form stains on the surface of stainless steel. However, this can be easily managed through various cleaning and maintenance methods.
Pricing instability: Very often copper is more expensive than stainless steel. However, it is the instability of its pricing that can cause issues to a project rather than its high pricing.
Discolouration: Copper can lose or change colour over time. If it is a specific finish that is required, then regular maintenance is necessary. A good reference would be the “new penny” look.
Vulnerability: As copper is a softer metal, it can be vulnerable during application, especially where cooling is required to complete the work.
Less corrosion resistant: It is less resistant to corrosion than stainless steel.
Extreme temperature vulnerability: Copper piping have difficulty withstanding extreme cold.
Needless to say, with all projects, different materials suit different requirements. If you’re after the high thermal conductivity for quick heat transfer, then copper is your option. If you’re looking for marine grade corrosive resistant piping, then stainless steel would be your best bet.
With over 25 years in the industrial piping and fittings business, we often have customers consider both options for their projects. But due to the forever fluctuating pricing of copper, and the demonstrated capabilities of its materially stronger counterparts, it is too hard to go past good old stainless steel.