Welding Recommendations

Carbon Steel Vessels in Caustic Soda Solution Service
Caustic soda solution users are responsible for building and maintaining a properly designed storage and handling system which meets applicable safety and regulatory requirements. Each caustic soda solution user is responsible for determining the preparation and welding techniques that are suitable for its individual facility.

Welding Preparation: Drying, Cleaning and Grinding

Immediately prior to initiating a welding or heating procedure, the weld area should be cleaned, for a distance of at least 6-inches (15-cm) out from the edges of the repair, with a suitable low sulfur solvent cleaning solution. All oil, paints, greases, marking crayons, cutting fluids, solder, lead (such as hammer marks) should be removed from the area to be heated.
Material cleanliness is a very important requirement for successful welding, especially when welding nickel and nickel alloy materials.
All metal surfaces to be welded should be dry prior to any welding.
Grind or power-brush until clean, all areas to be welded. Nickel and nickel alloys should be cleaned with a stainless steel wire brush. All cleaning tools including wire brushes and carbide grinding tools should be clean and free of debris or other metal fragments.

Listed below are additional guidelines to follow prior to welding on a carbon steel vessel used in caustic soda solution service:

Carbon steel is subject to caustic stress corrosion cracking. Stress crack initiation is a function of both temperature and concentration, with one limit being nominal 120°F (49°C) for 50% caustic soda solution and another limit at 175°F (79°C) for 10% caustic soda solution. Reference the Caustic Soda Service Graph (33KB PDF) for more information. Welds and steel bend areas should be stress relieved if service conditions are anticipated to exceed 120°F (49°C) for 50% caustic soda solution.
Caustic soda solution residue must be cleaned from the metal before a suitable weld can be made. If residual caustic soda is not removed, cracks will propagate as the weld is made. Catastrophic failure of the metal may occur during welding if the area is not properly cleaned prior to welding.
Repair of a weld area should proceed only after the old weld is ground smooth and cleaned.
Hydrogen is a corrosion product in aqueous services. It is important to consider the potential presence of hydrogen before cutting, grinding, burning or welding on any equipment recently removed from service. Welding should take place only in well ventilated areas.
The weld must be made with suitable welding rods, such as those containing 0.5% molybdenum for carbon steel.
The completed weld should be inspected by dye check.

Note of caution: The heat of grinding may create and propagate crack-like defects in caustic soda contaminated metal. Some defect examination methods include:

Ferromagnetic materials: Magnetic particle examination of ground surfaces prior to welding is recommended, if grinding is required.
Non-ferromagnetic materials: A liquid penetrant examination of ground surfaces prior to welding is recommended, if grinding is required. Any crack-like indications revealed by these examinations indicate the cleaning process was not adequate and the metal surface should be thoroughly cleaned again.

The information contained above is supplemental to the Internet Disclaimer and is not intended to be all-inclusive as it relates to use, handling, storage, disposal and all other described activities. Recipients must make their own determination of suitability and are responsible for compliance with all applicable federal, state, provincial, municipal laws and/or other regulations. This information is offered solely for your consideration and verification and in no event will The Dow Chemical Company be responsible for damages of any nature whatsoever resulting from the use or reliance upon this information or the product to which this information pertains.


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Each caustic soda solution user is responsible for determining the preparation and welding techniques that are suitable for its individual facility. Welding Preparation: Drying, Cleaning and Grinding Immediately prior to initiating a welding or heating procedure, the weld area should be cleaned, for a distance of at least 6-inches (15-cm) out from the edges of the repair, with a suitable low sulfur solvent cleaning solution. All oil, paints, greases, marking crayons, cutting fluids, solder, lead (such as hammer marks) should be removed from the area to be heated. Material cleanliness is a very important requirement for successful welding, especially when welding nickel and nickel alloy materials. All metal surfaces to be welded should be dry prior to any welding. Grind or power-brush until clean, all areas to be welded. Nickel and nickel alloys should be cleaned with a stainless steel wire brush. All cleaning tools including wire brushes and carbide grinding tools should be clean and free of debris or other metal fragments. Listed below are additional guidelines to follow prior to welding on a carbon steel vessel used in caustic soda solution service: Carbon steel is subject to caustic stress corrosion cracking. Stress crack initiation is a function of both temperature and concentration, with one limit being nominal 120°F (49°C) for 50% caustic soda solution and another limit at 175°F (79°C) for 10% caustic soda solution. Reference the Caustic Soda Service Graph (33KB PDF) for more information. Welds and steel bend areas should be stress relieved if service conditions are anticipated to exceed 120°F (49°C) for 50% caustic soda solution. Caustic soda solution residue must be cleaned from the metal before a suitable weld can be made. If residual caustic soda is not removed, cracks will propagate as the weld is made. Catastrophic failure of the metal may occur during welding if the area is not properly cleaned prior to welding. Repair of a weld area should proceed only after the old weld is ground smooth and cleaned. Hydrogen is a corrosion product in aqueous services. It is important to consider the potential presence of hydrogen before cutting, grinding, burning or welding on any equipment recently removed from service. Welding should take place only in well ventilated areas. The weld must be made with suitable welding rods, such as those containing 0.5% molybdenum for carbon steel. The completed weld should be inspected by dye check. Note of caution: The heat of grinding may create and propagate crack-like defects in caustic soda contaminated metal. Some defect examination methods include: Ferromagnetic materials: Magnetic particle examination of ground surfaces prior to welding is recommended, if grinding is required. Non-ferromagnetic materials: A liquid penetrant examination of ground surfaces prior to welding is recommended, if grinding is required. Any crack-like indications revealed by these examinations indicate the cleaning process was not adequate and the metal surface should be thoroughly cleaned again. The information contained above is supplemental to the Internet Disclaimer and is not intended to be all-inclusive as it relates to use, handling, storage, disposal and all other described activities. Recipients must make their own determination of suitability and are responsible for compliance with all applicable federal, state, provincial, municipal laws and/or other regulations. This information is offered solely for your consideration and verification and in no event will The Dow Chemical Company be responsible for damages of any nature whatsoever resulting from the use or reliance upon this information or the product to which this information pertains.
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