7. All metals have properties that cause them to react as an anode or a cathode when coupled to another material in a corrosive environment. The application of zinc (anodic coating) to iron substrates forms a protective layer and results in a corrosion protection referred to as cathodic protection or sacrificial protection. The substrate iron becomes the cathode and the zinc coating becomes the sacrificial anode.

8. The typical process temperature for the aluminizing process is between 9000C and 10500C.

We note below brief details of the tests carried out on zinc and aluminized coating surfaces :

1. THICKNESS OF COATING : This test is carried out to ensure that the coating provided is to the accepted standards. A self calibrated coating thickness gauge (Elcometer - Model No. 456) with test pieces is used for testing the thickness of Zinc/Aluminium Coating as per IS: 3203:1982.

2. BOND TESTS : This test indicates the mechanical bonding of Zinc/Aluminium coating to the substrate. This is carried out by using an imported special Bond Tester as per ASTM-D 4541-1985. A dolly is fixed on a sample piece using an adhesive material and by forcing it to be pulled out by using the Bond Tester called Elcometer 106. The load at which this dolly gets seperated from the test piece indicates the bonding strength in terms of PSI (Pound Per Square Inch).
Secondly by using a scriber, severeal lines at close intervals are drawn on the coated surface as per IS: 5905. The coating along the lines should not peel-off.