noun
inhibitor; preventive agent
A substance or agent that prevents something, often used in technical or medical contexts (e.g., rust inhibitor, corrosion inhibitor).
この塗料には錆防止剤が含まれている。
This paint contains a rust inhibitor.
冷却水に腐食防止剤を添加する。
Add a corrosion inhibitor to the cooling water.
Compound of 防止 (prevention) + 剤 (agent, chemical).