1- 6 HCl + Fe 2 O 3 ----- 2 FeCl 3 + 3 H 2 O 2- Fe + HCl -------- Fe Cl 2 + H 2 The main concentration of pickling tank is 16% wt/ wt . The performance of the tank can't be effective when it reaches 5 wt/ wt . At this point the iron content is 150 gr / lit . it means you have ore or iron mine . There is more than one option to treat this consumed acid : · Acid Regeneration : it can be used on or off line by using special type of resins in order to get rid of iron then concentrate it to reach crystal stage as FeCl 3 and it is necessary to keep Fe content within 10 gr/ lit to reduce dipping time in pickling or acid tank . the second option to treat the consumed acid off line by evaporation or treat it with sulfuric acid as below 3 H 2 SO 4 + 2 FeCl 3 ------ 6 HCl + Fe 2 ( SO 4 ) 3 H 2 SO 4 + FeCl 2 ------ 2 HCl + Fe SO 4 The value of ferric sulfa
There are two factors to be considered : 1 - The iron for galvanizing is a product and not galvanized for the purpose of maintenance. 2- If the option to choose the metal exists, it is desirable to choose iron that gives us a high quality product within the basic criteria, including: 1- The chemical composition of the metal, especially the content of silicon, carbon and phosphorous .... etc . 2- The surface must be free of organic pollutants (dyes, paints, polymers, bitumen). 3- No high corrosion or pores in the metal surfaces . 4- The thickness of the iron should be consistent and no significant differences. 5- The design of products should allow draining of molten zinc.
A- degreasant 1- Degreasing: It is used to remove organic substances or contamination , the concentration of this material usually 10% wt/wt from tap water 2- Actually 7.5% has been used in decreasing tank the, the process take place without problem in production 3- The temperature of the tank is 75 c, there are neutral , alkaline and acidic degreaser . 4- The dipping time is the same . 5 - The method of check the concentration is necessary to improve performance and to control . B- pickling additive 1- This additive is used as: a- inhibitor agent b- wetting gent c- anti – vaporization agent 2- 1.4% of the concentrated acid is added to the pickling tank from the pickling additive 3- The use of the pickling additive has taken place with out any problems 4- they are harm ful in case of producing new substances from consumed acid , and same for water treatment ( almost contain heavy metals and
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