1. Thermal spray coatings are widely used in preventing corrosion of many materials. A common application is the use of zinc to protect iron substrates. In this method, the surface of the metal is prepared by abrasive blast cleaning to ensure it is cleaned and roughened. Metal wire or powder is fed at a controlled rate into a flame or arc spraying process and the atomized metal impinges upon the surface being coated and becomes bonded to it. This process is easily adapted to production environments.
2. Good mechanical interlocking provided the abrasive grit blasting pretreatment is carried out correctly.
3. Thickness variable at will generally 100 - 150 microns but coatings of up to 500 microns can be applied.
4. The Aluminizing process is used to protect parts operating in high temperature environments against corrosion and oxidation. As a result, the most common parts coated are high temperature industrial chimney and muffler.
5. Coating with sealants that can provide a base for paints to give long life structures.
6. The ability to control the coating thickness and superior adhesion of the zinc to the iron substrate
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.
3. PRECESSION TEST FOR UNIFORMITY OF COATING (IS:2633) : In this instance the sample piece is subjected to dipping in Copper Sulphate Solution four times and each dipping will be of one-minute duration. After the fourth dip, the sample is checked for any red coloration on the surface. Cooper deposition takes place in areas where coating is not uniform.
4. PURITY OF ZINC / ALUMINIUM : We are getting Zinc/Aluminium wire tested in an external lab to ascertain the purity of Zinc, which should be 99.95% as per IS: 209. A certificate to this effect can be provided to the customer along with our test certificate if desired
STRESS RELIEVING /Alluminizing /metallizing.