| INTRODUCTION This specification covers, 'Etching Primer' to be used specifically for Engineering units. It covers basic know-how of the primer properties, application and advantages. This is two component system. Base is based on polyvinyl Acetyl Resin say Polyvinyl Butyral one. Polyvinyl Resin gives water resistance through its paraffin structure while dioxin link nucleus of six atoms give rise to a noticeable chemical resistance. Resin solution is clear, colourless gives excellent hardness and flexibility to the film. ETCH PRIMER is also known as WASH PRIMER and referred to as metal conditioners. Compared with other corrosion inhibiting materials, they are unique and most effective because they offer in a single treatment several means of preventing corrosion. It gives excellent adhesion to many substrates; faster drying is also advantageous. The action of Etch Primer over steel or say, for example metal is three folds : Firstly an Iron oxide and Zinc phosphate film similar to that formed in common phosphating process is deposited on the metal. Secondly this primer also provides a continuous supply of chromate ions for the repair of any pinholes present in the phosphate film. Special chromate rinse is eliminated. And thirdly the Polyvinyl Butyral or formal film is chemically bound in the organic layer through a chromium complex, thus providing additional mechanical protection to the metal surface. 2. THE RANGE OF APPLICATION This primer is used for storage Tanks, Ships, Airplanes, Bridges, Dam locks, Agricultural equipment's, etc. Etch Primer is applied in all cases where paint coating require weathering, seawater resistance and on damp metallic surfaces. It is having excellent heat resistance and on damp metallic surfaces. It is having excellent heat resistance up to 400o C. 3. KEY PROPERTIES OF SYSTEM * Fast drying at room temperature or low temperature baking. * It can withstand up to 400o C. * Phosphating and Chromate rinsing can be eliminated in pretreatment. * Excellent weather and water resistance. * Very good resistance to solvents. * Adhesion to many substrates, Fibreglass sheets, Aluminium, Steel, and M.S. * Effect under welding . (See product data ) * Excellent water and alkali resistance. Resistance to mild acids. Not recommended for direct immersion. * Any type of topcoat is suitable. * Unaffected by Oil & Grease. 4. APPLICATION : Efficient degreasing must be done. If there is heavy rusting on M.S.use de-rusting chemical. No other treatment is necessary . Stir base component thoroughly before mixing. Take equal parts of Base Hardener in a container. After mixing allow it to mature for 15-20 minutes and then stir before use. It is particularly important that film thickness should not exceed more than 8 microns. So application by conventional spray is advisable. Application by brush, spray or roller is also possible. No thinner should be added while spraying. Use an atomizing pressure of 2.8 to 3.0 kg/cm. Do not apply when temperature is below 10 C or when relative humidly rises above 90 % or during rain, fog or mist. Brushes and spray equipment's should be cleaned immediately after use with TUFF COATS THINNER TC/NC-102 ; otherwise equipment is liable to be damaged. |