Screws are brightly colored. Screw fasteners of various colors, such as silver, black, yellow, purple, and so on, can be found everywhere. So, how did these multicolored screws come to be? Screw plating is a procedure that adds vibrant colors and beauty to screw fasteners.
Screw plating is used for colored products
The screw is quite greasy and unclean when it is freshly manufactured. At this moment, it must be brought to an electroplating plant to be made attractive and functional. The color of the screw electroplating can be matched with the color of the material. When a screw fastener is plated, it takes on a more colorful and bright appearance.
Screw plating is available in white zinc, blue zinc, colorful zinc, white nickel, black nickel, black zinc, and green.
What should be paid attention to during the screw plating process?
1. If screws with different specifications mix together for electroplating, some areas cannot be plated, resulting in product scrapping. Before electroplating, the screws must be cleaned.
2. It is difficult to achieve the quality requirements of electroplating layers and diverse specifications, such as the appearance color and screw properties, under the process conditions of conventional electroplating, most of which require professional operation.
3. Screw specs are too near, for example, the size and length appear to be the same. This type of screw plating should be done separately; otherwise, it is difficult to screen.
4. Plate heavier screws and lighter screws separately. To electroplate, smaller and larger screws should be separated. Otherwise, screws of various specifications and models become locked together during the electroplating process, causing harm to the screw.
5. The screws are easily electrocuted when they become trapped together. Otherwise, the two distinct specifications and models of screws become entangled, which quickly leads to plating failure, even after the screw plating has been completed. It is also difficult to separate different types of screws.
Quality control methods of screw plating product
The key measurement standard for screw plating quality is corrosion resistance and attractiveness. The corrosion resistance is designed to mimic the product's environment. Set the test settings to the environment and conduct the corrosion test. So, what are the quality assurance procedures for screw electroplating products?
1. Appearance
The screw's entire surface must be coated. Scorching, roughness, grayness, peeling, crusting, visible stripes, pinholes, loose passivation film, cracking, and severe passivation traces are not permitted.
2. The thickness of the plating
In a corrosive environment, the service life of a self-tapping screw is directly proportional to the plating thickness. Hot-dip galvanized has an average thickness of 54um and a minimum thickness of 43um.
3. Distribution of plating
The plating aggregation technique on the fastener surface differs. The plating metal is not consistently deposited on the edge of the outer peripheral while plating. To achieve a thicker plating at the corner, various accumulation processes are used. The screw's thickest plating is at the top of the thread, gradually becoming thinner at the front of the thread, and thinnest at the bottom. Hot dip galvanizing is the polar opposite. The inner corner and bottom of the thread receive thicker plating. Mechanical plating has the same metal accumulation propensity as hot dip plating, but it is considerably smoother and the thickness of the overall appearance is much more consistent.
4. Emrittlement due to hydrogen
When fasteners are processed, particularly during the pickling and alkaline processes before to plating and subsequent electroplating, the appearance absorbs the hydrogen atom, and the accumulated metal plating captures hydrogen. When the screw is tightened, the hydrogen moves to the most concentrated region of the stress, causing the pressure to rise to levels that exceed the strength of the base metal, resulting in a little appearance fracture. Hydrogen is especially aggressive and quickly enters into newly created cracks. This cycle will continue until the fastener snaps. It usually happens within a few hours of the first stress. To reduce the risk of hydrogen embrittlement, the fastener should be heated as soon as possible after plating to allow the hydrogen to be expelled from the plating. The heat treatment is normally performed for 3-24 hours. Mechanical galvanizing is non-electrolyte, hence the threat of hydrogen is eliminated.
Summary
Screw plating gives fastener products vivid colors, making them beautiful, colorful, and gorgeous. What should be paid attention to throughout the electroplating process and how to control the quality of the screw products are major concerns. The article provides some important information for improving the effect of screw plating.
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