Electroplating is a common method of surface treatment of fasteners such as metal screws. Under normal circumstances, the quality of electroplating is mainly measured by its corrosion resistance, followed by appearance. Corrosion resistance is to imitate the working environment of the product, set as the test condition, and conduct corrosion test. The quality of metal screw product plating is controlled from the following aspects:
1. Appearance: The surface of the metal screw products is not allowed to be partially uncoated, burnt, rough, gray, peeling, crust and obvious stripes. Pinhole pitting, black plating, loose passivation, turtle are not allowed. Cracking, shedding and severe passivation marks.
2. Hydrogen embrittlement: During the processing and processing of metal screw fasteners, especially during pickling and caustic washing before plating and subsequent electroplating, the surface absorbs hydrogen atoms, and the deposited metal plating layer then captures hydrogen. When the fastener is tightened, hydrogen is transferred to the most concentrated portion of the stress, causing the pressure to increase beyond the strength of the base metal and creating a slight surface crack. Hydrogen is particularly active and quickly penetrates into newly formed fissures.
3. Plating distribution: Different deposition methods are used, and the plating layer is different on the surface of the fastener. When the metal screw fastener product is plated, the plated metal is not uniformly deposited on the peripheral edge, and a thicker coating is obtained at the corner. In the threaded portion of the fastener, the thickest coating is located on the crest of the thread, gradually thinning along the side of the thread, depositing the thinnest at the bottom of the tooth, while hot dip galvanizing is just the opposite, thicker coating is deposited inside the corner and At the bottom of the thread, the mechanical plating of the plated metal tends to be the same as that of hot dip coating, but is smoother and much more uniform over the entire surface.
4. Coating thickness: The working life of metal screw fasteners in corrosive atmosphere is proportional to the thickness of its coating. The recommended economical plating thickness is 0.00015 in to 0.0005 in. (4 to 12 um). Hot dip galvanizing: the standard average thickness is 54 um (the nominal diameter is ≤ 3/8 is 43 um), and the minimum thickness is 43 um (the nominal diameter ≤ 3) /8 is 37um).
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Steel poles are commonly used to carry several types of electric power lines, distribution lines and lighting system. Distribution lines carry power from local substations to customers. They generally carry voltages from 4.6 to 33kV for distances up to 30 miles, and include transformers to step the voltage down from the primary voltage to the lower secondary voltage used by the customer. A service drop carries this lower voltage to the customer's premises.
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