We are the only fastener manufacturer in India who are doing high Temperature galvanizing. using Morganite Ceramic Crucible .

Comparison Between Conventional Galvanizing & high Temperature Galvanizing: In high Temperature galvanizing it is essential to operate temperature above critical range of 480-520 C. where the rate of the attack by Zinc on Steel is very rapid and shows a distinct peak. This serves as the demarcation between conventional galvanizing, which is normally carried out at 460-560 C. As the solubility of Iron in Zinc at that high temperature is much higher (about 0.3% compared to the preferred range of 0.1 % for proper galvanizing.), the conventional design using Steel Kettle is not suitable. Consequently a ceramic lined top fired design is normally resorted to.

Finish as compared with conventional Galvanizing: In conventional galvanizing process continuous generation of the Dross takes place due to Zinc attack on the Steel Kettle (in addition to the normal process of Dross formation due to immersion of Steel parts to be galvanized. The presence of pimples and entrapped Dross particles on the surface of the galvanized Bolts renders the coating layer discontinuous and hence inconsistent. The products galvanized in high temperature galvanizing bath have a smooth matt grey finish. It will be observed that there is no trace of lumpiness or pimples on the surface due the absence of Zeta layer during high Temperature Galvanizing.

Behavior in Preece Testing:

In an experiment it is evident that in most cases, conventional galvanized samples have with stood 4 dips in the preece test and failed after fifth dip. Inspite of the generally high coating thickness, none of the samples withstood a preece dip of 5.This implies demonstrates the absence of uniformity of coating in conventional galvanizing. However in high temperature galvanizing a definite correlation is seen to exist between the coating weights and the number of Preece dips withstood by the sample. The high temperature galvanized samples are generally seem to have withstood more dips for the same or lower coating thickness-which can be explained by greater uniformity of the coating achieved and absence of pimples.This also demonstrates a higher level of corrosion resistance from the ,measured coating thickness values.

 

The important effect of high temperature galvanizing is the elimination of the Sandelin phenomenon. The Sandelin phenomenon can be interpreted based on the Kinetics, Morphology and thermodynamics of Galvanizing, showing that the first intermettalic compound to precipitate at 450 C during the steel Zinc Reaction is the zeta Phase. Then the Iron Diffusion varies from the parabolic law with low silicon content steels to a linear independence with Sandelin steels. Since the Zeta intermetallic compound disappears above 530 C., the first inter metallic compoundto precipitate during the zinc steel Reaction at high temperature is the Delta Rich Phase. Thus disappearance of Sandelin phenomenon is established in high temperature galvanizing.