25%鹽酸用于 initial rust removal, soak the rusty screws until the rust is completely gone and the white metal body of the screw is exposed. Then, use a mixture of 50% hydrogen peroxide and 98% hydrofluoric acid in a ratio of 1 to 6. Soak the cleaned screws in the acid solution for about 3 to 5 seconds, remove quickly, and wash with clean water. Next, soak the screws in hydrochloric acid for another 3 to 5 seconds, followed by a thorough rinse with clean water. 2. Screws are tools that utilize the principles of physics and mathematics, specifically the rotation of an inclined plane and friction, to gradually tighten and secure objects. They are commonly referred to as fasteners and are an essential part of various devices and structures. In engineering, construction, and bridges, large screws and nuts are used, while in automobiles, aircraft, and other transportation devices, a combination of small and large screws are employed. Screws play a vital role in the industrial sector and will always be important as long as industry exists on Earth. They are a collective invention of humanity over thousands of years and are considered one of the greatest inventions, given their wide-ranging applications. The primary function of screws is to join two objects together and provide a tightening force.