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C-steel: 5 steps to a solid installation

Carbon steel pipes and fittings are often used in heating and cooling water systems. Under certain conditions corrosion has occurred in the past. However, following a few criteria, this can be prevented easily, as carbon steel is a solid material for the right application. This article shows you what you need to consider to prevent corrosion.


Carbon steel (c-steel) pipes and fittings are very attractive from an economic point of view. Observing a few key points, installers have an ideal material for all closed systems, i.e. piping systems without a permanent or regular oxygen supply. Anyone familiar with proven installation technology can offer their customers a reliable heating or cooling system at a favourable price with this material when they follow these steps.

5 steps for a long-lasting C-steel piping system

1. Storage and transport:

Both must be done in such a way that the pipes and fittings are protected from moisture.

2. Observe area of application:

Pipe systems made of carbon steel can easily be used for all internal pipes in closed systems. This means: No external installation, no chemically aggressive atmosphere and no permanent entry of oxygen into the system. Both the flow and the return of heaters can be made of carbon steel. Closed cooling water systems can also be installed with this material. If the pipe could come into contact with water (e.g. screed, condensation water, damp masonry), it must be protected against external corrosion.

3. Protecting connections:

If possible, connections for a radiator should not be routed upwards from the floor but directly into the wall via a wall connection box with integrated condensation water protection. Neither plaster water nor moisture in the masonry can then reach the carbon steel at the most critical points.

4. Correct pressure test:

First pressure tests should be with dry compressed air at appropriate stages of the construction. Water should only be used for testing once the system is ready to be commissioned.

5. Commissioning:

Prior to operation, a system needs to be flushed. This is designed to remove any loose particles of swarf or debris, introduced into the system during assembly. In all instances, the flushing and commissioning of the system should be carried out as per the M&E consultant’s specification. Guidance on commissioning and flushing can be found in CIBSE AM14:2010.

Most carbon steel piping systems are galvanized on the outside or on both sides (not for heating). This layer, approx. 7 micrometers thick, offers a certain degree of protection according to EN ISO 2081 (stress level 1). These systems are therefore suitable for installation in warm and dry atmospheres. Brief humidification has no effect if the pipeline surface can then dry off quickly.

Pre-insulated C-steel systems hardly help

Pre-insulated systems are now available on the market. However, only the pipes are insulated. All fittings must subsequently be sealed, which is not only time-consuming. Gaps can easily be overlooked at this stage, or the insulation of the pipes can be damaged during transport or installation - an ideal spot for moisture to accrue from outside. In addition, it is often difficult to safely insulate the joints in narrow shafts, as there is simply no space available.

If a long-lasting or permanently humid environment is to be expected, a piping system made of low-alloy stainless steel such as NiroTherm from SANHA can be used as an economically and technically sensible alternative. This saves installers the time required for insulation and protects them from any possibly costly correction of construction faults due to corrosion.

Bottom line: C-steel works!

Piping systems made of carbon steel can be inexpensive and easy to process. This reduces the costs for construction projects and processors can submit competitive bids. Following a few simple steps can permanently protect the piping system from corrosion. During the construction phase, care must be taken to ensure that the installed pipes are stored or laid in dry environments, that penetrating water in the area of pipes is detected at an early stage and/or that the pipe surfaces are provided with effective corrosion protection. To achieve this goal, no new rules have to be created or new products developed, only known technical rules and specifications of the manufacturers have to be taken into account and adhered to.

Hand holding a carbon steel tee in a factory setting