Potassium silicate films are less hygroscopic and more resistant to moisture absorption than sodium silicate films at equivalent SiO₂:M₂O ratios. This makes potassium silicate the preferred binder in zinc-rich primer coatings for steel, high-temperature refractory cements, and welding electrode coatings where moisture pickup during storage would degrade performance. The choice between potassium and sodium silicate is therefore driven by end-use performance specifications rather than cost alone.

Line 2839901000 covers silicates specifically of potassium. If the product is a pure potassium silicate, it belongs there. Mixed alkali silicates (e.g., lithium-potassium or sodium-potassium blends) or silicates of other alkali metals (lithium, cesium, rubidium) that do not fit a more specific line would generally fall under the residual line 2839905000. The commercial invoice and product specification should clearly identify the alkali metal cation(s) to support the correct classification.