| Acid pickling procedure | Material contaminated by Oil, Grease or Paint, pre-treatment in special solvents will be necessary for their removal. Both Hydrochloric Acid / Sulphuric Acid solutions may be used for pickling. Both 100 – 150 g/l. This work handled in degreasing bath as to allow free circulation of liquid over all parts taking care to clean the scum. If necessary this work raised and lowered in order to allow the degreasing solution to enter inaccessible areas, threaded sections etc for a thorough cleaning action |
| Water Rinsing | Immediately after degreasing or acid pickling; material rinsed in hot (60*) water followed if necessary by a final rinse in cold running water. Material if not properly cleaned before annealing, develops burnton and patches at the surface. Which are not removed by normal pickling. Giving a quick rinse in running water followed by cleaning with one of the pickling acids. It is then processed according to normal fluxing practise |
| Flux Bath | The Rinsed material in the dry process is dipped in a strong solution of Zinc Ammonium Chloride. The actual concentration of the flux solution and its temperature depend on the work being under taken and on individual circumstances. The working level is generally between 200 to 400 g of zinc ammonium chloride per litre. The temperature may range from room temperature to 80*C. |
| Hot Plate | When dry galvanizing is adopted the material shall be thoroughly dried after Fluxing over a Hot plate. The temperature should be about 120* – 150* C. as the flux decomposes above this temperature. |
| Galvanizing | Zinc containing at least 98.5 % Zn to be used for the purpose of galvanizing. The molten metal in the galvanizing bath not contain less than 98% by mass of Zinc. The control of bath temperature is essential if the quality of the product is to be consistent. Material is galvanized at the suitable temperature which allows the free drainage of zinc from the work piece during withdrawal. A low temperature reduces the formation of ash and dross, besides safeguarding the pot and conserving fuel. The speed of immersion also influenses the uniformity of coating particularly with long work piece where the difference of immersion time between the first and the last part to enter the bath is being considered. In most of the time material shall be left in the bath until it reaches the temperature of the bath which is usually indicated by the stopping of the boiling action. It is then withdrawn without much delay |
| Withdrawal | The rate of withdrawal which determines the thickness of unalloyed zinc layer left on the article varies according to the type of the process being operated and the form of material. With long material for which withdrawal occupies a large part of the total handling time, speeds, are necessarily maintained at higher to ensure a reasonable rate of production. Special jigs and carriers has been used for dipping and withdrawing the work in batches. The rate of withdrawal is being controlled to drain the Zinc freely from the surface. |
| Water Quenching | Material after Flux bath gone through Quench water which has been changed frequently to prevent the accumulation of corrosive salts. Light gauge material is being spun quickly through the surface of water so that they retain sufficient heat after quenching to enable quick drying. Heavy gauge material retain sufficient heat for drying |
