3810.90.20.00 - Consisting wholly of inorganic substances

This HTS category, 3810.90.20.00, specifically covers pickling preparations, fluxes, and related soldering, brazing, or welding auxiliary materials that consist *wholly of inorganic substances*. This means that the composition of the product must be entirely inorganic, excluding any organic compounds or materials derived from living organisms. Examples within this category would include inorganic salts, oxides, acids, or other mineral-based compounds used for surface treatment of metals or as aids in joining metals.

It is crucial to distinguish this category from its siblings. HTS 3810.90.10.00 is for preparations containing 5 percent or more of aromatic or modified aromatic substances, inherently an organic component. Furthermore, HTS 3810.90.50.00 encompasses "Other" preparations within the broader Chapter 3810, suggesting it would capture inorganic preparations not fitting the specific criteria of 3810.90.20.00 or the aromatic exclusion of 3810.90.10.00. The defining characteristic here is the complete absence of organic matter in the formulation.

As this is a leaf node, there are no further subcategories under HTS 3810.90.20.00. Therefore, classification within this code relies solely on the definitive criteria of consisting wholly of inorganic substances and fitting the general scope of auxiliary preparations for soldering, brazing, or welding, or pickling preparations for metal surfaces. Proper identification of all constituent components is essential to correctly place goods under this specific tariff number.