Product classification
HS code for Welding flux: 3810.90
Fluxes and other auxiliary preparations, for soldering, brazing or welding, or preparations used as cores or coatings for welding electrodes or rods.
Classification of welding flux under HS 3810.90
Welding flux is classified under HS code 3810.90 because it is a chemical preparation designed to facilitate the welding, soldering, or brazing process. According to the Harmonized System, Chapter 38 covers miscellaneous chemical products. Heading 3810 specifically includes pickling preparations for metal surfaces, as well as fluxes and other auxiliary preparations for soldering, brazing, or welding. The subheading 3810.90 is a residual category for those preparations that do not consist of metal and other materials in the form of pastes or powders, which would otherwise fall under 3810.10. These fluxes are essential in industrial applications as they prevent the formation of oxides during the heating process, ensuring a clean and strong bond between the metal surfaces. They may be composed of various chemical compounds, including borates, fluorides, or silicates, depending on the specific welding technique and the metals being joined. The classification is determined by the chemical function of the product as a processing aid rather than a structural component. Under General Rule of Interpretation (GRI) 1, the product is classified by the terms of the headings and any relative section or chapter notes, which clearly point to Chapter 38 for these chemical mixtures.
- Covers
- Granulated flux for submerged arc welding (SAW)
- Flux powders for brazing and soldering
- Flux pastes used in electronics manufacturing
- Flux coatings for specialized welding electrodes
- Auxiliary preparations for cleaning metal surfaces prior to welding
- Also under 3810.90
- Kester Flux
- Alpha Assembly Solutions Flux
- Indium Corporation Flux
- Lincoln Electric Flux
- ESAB Welding Flux
Codes often confused with 3810.90
Common mistake. Welding flux is frequently misclassified under HS code 8311. This heading covers finished electrodes, rods, and wire of base metal that are already coated or cored with flux. If the flux is imported as a standalone chemical preparation, it must remain in 3810.90. Another common error involves HS code 3810.10, which is specifically for pickling preparations and soldering/brazing pastes consisting of metal and other materials. Pure chemicals, such as unmixed borax, should be classified in Chapter 28, specifically 2840, unless they have been specifically prepared and mixed as a fluxing agent.
Top exporters and importers of HS 381090 (the code used for welding flux), 2025
In 2025, the largest exporter of HS 381090 (the code used for welding flux) in UN Comtrade data was Germany, with 18% of world exports; the largest importer in UN Comtrade data was China, with 11% of world imports. Countries that did not report 2025 data are estimated from partner records, which can understate them.
Figures cover everything classified under HS 381090, not only welding flux.
Top exporters 2025 · share of world exports
- 1 Germany $164M 18% of world exports
- 2 Japan $159M 17% of world exports
- 3 China $86M 9.4% of world exports
World total: $921M Reported figures on UN Comtrade ↗
Top importers 2025 · share of world imports
- 1 China $120M 11% of world imports
- 2 Malaysia $105M 9.7% of world imports
- 3 Philippines $78M 7.2% of world imports
World total: $1.1B Reported figures on UN Comtrade ↗
How these figures are built
109 countries reported 2025 trade to UN Comtrade in HS 2022, and their own totals are used. Countries that did not report are estimated from what other countries recorded trading with them. Those estimates miss trade with other non-reporting countries, so they can be low, and a non-reporting country can rank higher than shown or be missing from the list. World totals add both and leave out trade between two non-reporting countries. Figures are in current US dollars; reported imports are mostly valued CIF and exports FOB, and exports include re-exports. The UN Comtrade links show the underlying records; they can also list a few reporters left out here (regional groups and older HS editions).
Source: UN Comtrade (United Nations Statistics Division), 2025 annual data.
Brazil NCM code for welding flux
Brazil classifies welding flux under NCM 3810.90.00: HS 3810.90 with 00 added.
Source: Siscomex NCM table, updated Oct 2026. The Portuguese text on each NCM page is the official one.
Questions about welding flux
What is the HS code for Welding flux?
The HS code for Welding flux is 381090 (Fluxes and other auxiliary preparations; for soldering, brazing or welding, or preparations used as cores or coatings for welding electrodes or rods). The HS code for welding flux as a standalone chemical preparation is 3810.90.
How do I classify Welding flux for customs?
Welding flux is classified under HS code 381090 — Fluxes and other auxiliary preparations; for soldering, brazing or welding, or preparations used as cores or coatings for welding electrodes or rods. This is a 6-digit subheading level code.
Does this code include the metal welding rod?
No, metal welding rods that are coated or cored with flux are classified under heading 8311, specifically 8311.10 for arc welding or 8311.30 for flame welding.
Which countries are the top exporters of welding flux (HS 381090)?
In 2025, the top exporters of HS 381090 (the code used for welding flux) in UN Comtrade data were Germany ($164M, 18% of world exports), Japan ($159M) and China ($86M). World exports came to about $921M, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.
Which countries are the top importers of welding flux (HS 381090)?
In 2025, the top importers of HS 381090 (the code used for welding flux) in UN Comtrade data were China ($120M, 11% of world imports), Malaysia ($105M) and the Philippines ($78M). World imports came to about $1.1B, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.
Is the HS code for Welding flux the same in all countries?
The base HS code 381090 for Welding flux is internationally standardized for the first 6 digits across 200+ countries. Individual countries may add additional digits for national tariff lines and specific classifications.
What is the NCM code for welding flux in Brazil?
In Brazil, welding flux (HS 381090) is classified under NCM 3810.90.00.