We operate a centrifuge (Spinning) fastener, screw, bolt and nut galvanizing facility at Shah Alam and the plants process fasteners, screws, bolts and nuts:
1) Bolts, nuts, washers and other small parts which requires the centrifuged hot dip galvanizing process. Spinning removes all excess residual zinc from the threads of bolts. Oversized nuts fitted perfectly for very small parts.
2) Threaded bolts (M32 x 1m) centrifuged hot dip galvanied with special cylindrical jigs produced very clean threads free form all residual excess zinc. The oversized nuts fitted perfectly. No additional thread cleaning services were necessary.
HOT DIP GALVANIZING FOR BOLTS, NUTS AND FASTENERS
Bolting of Steel Structures
Normally for a non galvanized steel structure individual steel components are either welded or hot riveted. Hot dip galvanized bolts and nuts are essential for the construction of hot dip galvanized steel structures. In fact bolting of steel structures are now widely used as it is easy and versatile to move and construct huge steel structure anywhere.
The Centrifuged Hot Dip Galvanized Bolts and Nuts
Hot dip galvanized bolts and nuts are normally centrifuged immediately upon removal from the molten zinc. Compared to other forms of corrosion protection such as electroplating the centrifuged or spin hot dip galvanizing process produces a heavier zinc coating. This zinc coating is metallurgically formed and is bonded to the base steel and is a succession of metallurgically formed zinc alloy layers namely Zeta, Delta and Gamma layers with an outer Eta pure zinc layer.
The centrifuging process removes the free zinc outer Eta layer producing clean and smooth threads. There are two types of spinners commonly used in galvanizing plants and they are either the floor mounted type or above the above the bath spinners.
The Centrifuged Hot Dip Galvanizing Standards
Most of the hot dip galvanizing standards specify that centrifuged hot dip galvanized material must achieve a minimum coating mass of 300 g/m2. For hot dip galvanized nuts it is essential that threads are tapped only after the hot dip galvanizing process. The internal threads should also be oversized to compensate for the increase in zinc coating thickness of the threads. Typically oversizing are in the range of 0.4 mm for M24 to 1.0 mm for M46 onwards.
In the relevant standards such as ASTM 123/A123-97a the minimum coating mass for materials that are centrifuged hot dip galvanized is 320 grams per square meters. (45 microns) for M20 threads to 140 grams per square meters (gm/m2) or 140 microns for M6 threads.
Centrifuged Hot Dip Galvanized Bolts Nuts and Other Threaded Fasteners
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