Preliminary Requirements

Safety Requirements

WARNING

IT IS THE RESPONSIBILITY OF THE OPERAOR TO OBTAIN AND OBSERVE THE MANUFACTURERS MATERIAL SAFETY DATA SHEETS FOR CONSUMABLE MATERIALS INFORMATION SUCH AS, HAZARDOUS INGREDIENTS, PHYSICAL/CHEMICAL CHARACTERISTICS, FIRE EXPLOSION, REACTIVITY, HEALTH HAZARD DATA, PRECAUTIONS FOR SAFE HANDLING, USE AND CONTROL MEASURES AND ALSO TO TAKE LOCAL REGULATIONS INTO CONSIDERATION.

WARNING

CHROMIC ACID IS VERY DANGEROUS. IF BREATHED, IT WILL CAUSE ULCERS IN THE NOSE AND IT CAN CAUSE DAMAGE TO THE NASAL SEPTUM. CHROMIC ACID SALTS AND SOLUTIONS, THAT TOUCH THE SKIN, CAN CAUSE CHROME SORES. THEY CAN ALSO CAUSE ULCERS, IF THEY GET INTO CUTS AND ABRASIONS.

THE CHROMIUM ACID BATH MUST NOT BE USED, UNLESS THE FUME EXTRACTOR IS OPERATED AND IS FULLY SERVICEABLE.

A RECOMMENDED BARRIER CREAM MUST ALWAYS BE APPLIED, TO THE HANDS AND FOREARMS, BEFORE WORK IS STARTED.

PROTECTIVE CLOTHING MUST ALWAYS BE WORN.

DO NOT EAT OR SMOKE, NEAR THE CHROMIUM PLATING BATH.

IF CUTS AND ABRASIONS DO NOT HEAL SATISFACTORILY, TELL THE MEDICAL DEPARTMENT.

CHROMIC ACID SOLUTION CAUSES OXIDATION AND IS A FIRE RISK, BECAUSE OF THE POSSIBLE SPONTANEOUS COMBUSTION OF ORGANIC MATERIALS - (SUCH AS CLOTH AND WOOD), SOAKED BY THE SOLUTION. SUCH DIRTY MATERIALS MUST BE SOAKED IN SODIUM BISULPHATE SOLUTION TO MAKE NEUTRAL THE CHROMIC ACID, THE SOLUTION MUST THEN BE DISCARDED AS SPECIAL UNWANTED MATERIAL. THE SOLID MATERIAL MUST THEN BE FLUSHED WITH WATER BEFORE IT IS DISCARDED.

WARNING

EVERY POSSIBLE CARE MUST BE TAKEN TO AVOID THE SOLUTION COMING INTO CONTACT WITH THE EYES OR BARE SKIN. PROTECTIVE CLOTHING INCLUDING RUBBER GLOVES AND GOGGLES MUST BE PROVIDED FOR THE OPERATORS WHEN PREPARING AND USING THE NITRIC AND SULFURIC ACID SOLUTION. RUBBER GLOVES SHOULD BE CHECKED REGULARLY FOR PIN HOLES AND REPLACED IF NECESSARY.

SAFETY NOTICES MUST BE PLACED IN A CONSPICUOUS PLACE.

EYE-WASH BOTTLES AND HF BURN JELLY MUST BE PROVIDED AS CLOSE AS POSSIBLE TO THE PLACE OF WORK.

IF SKIN BECOMES CONTAMINATED WITH THE SOLUTION IT MUST BE RINSED WITH COPIOUS AMOUNTS OF CLEAN RUNNING WATER.

ALL BURNS, HOWEVER SLIGHT, SHOULD BE TREATED AT THE NEAREST SURGERY OR FIRST AID POST.

THE SURGERY MUST BE TOLD WHICH SOLUTION (THE ACIDS INVOLVED) HAS CAUSED THE BURN.

Procedure

1. SUBTASK 70-33-20-200-001 Control of the Chromic Anodizing Solution

   1. Control of Solutions.

      1. The solution must be analyzed regularly, depending on the work-load, to make sure that the electrolyte is maintained within the following limits:

         1. Free chromic acid: 4.8 to 8.0 oz/gal (30 to 50 g/l).

         2. Chloride - (As NaCl): 0.03 oz/gal (0.2 g/l) maximum.

         3. Sulfate - (As Na2S04): 0.08 oz/gal (0.5 g/l) maximum.

      2. CoMat 01-023 CHROMIUM TRIOXIDE CrO3(CHROM.ACID) can be added when the above limits are maintained and the total chromium (estimated as potassium dichromate) is not more than 16 oz/gal (100 g/l). When solution contains more than 16 oz/gal (100 g/l) potassium dichromate, it is necessary to discard the solution.

   2. Analysis of unused solutions for free chromic acid.

      NOTE

      It is necessary to do a check of the solution for free chromic acid content, before use and regularly during its life.

      1. Refer to TASK 70-11-47-110-501, SUBTASK 70-11-47-180-036.

   3. Analysis of unused solutions for potassium dichromate.

      1. Use a safety pipet to transfer a 20 ml cooled sample, into a 200 ml volumetric flask. Add CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER, to the mark, then fully mix. Pipet a 10 ml sample, of this solution into a beaker or a conical flask.

      2. Dilute with distilled or deionized water to approximately 50 ml, then add 10 ml of a 50 percent solution of CoMat 01-043 SULFURIC ACID H2SO4.

      3. Use a buret to add 19.5 ml of an N/10 solution of CoMat 01-054 FERR.AMMON.SULPHATE FeSO42S04 6H2O. Quickly titrate with an N/10 solution of CoMat 01-055 POTASSIUM PERMANGANATE KMnO4 to a pink end-point.

      4. NOTE

         The total amount of potassium permanganate used in the titration, is represented by T1 in the formula below.

         Add a further 0.5 ml of the N/10 solution of ferrous ammonium sulfate. Titrate with the N/10 solution of potassium permanganate, in drops, to a faint purple end-point.

      5. Carry-out a blank determination with each analysis:

         1. Pipet 10 ml of distilled or deionized water into a beaker, then add 10 ml of the 50 percent sulfuric acid solution.

         2. Add 19.5 ml of the N/10 ferrous ammonium sulfate solution from a buret, then quickly titrate with the N/10 potassium permanganate solution to a pink end-point.

         3. Add a further 0.5 ml of the N/10 ferrous ammonium sulfate solution then titrate with the N/10 potassium permanganate solution, in drops, to a faint purple end-point.

      6. Therefore, (T2 - T1) x 4.9 = g/l of potassium dichromate.

   4. Analysis of used solutions.

      1. NOTE

         This procedure is applicable only to used solutions that contain aluminum, trivalent chromium, and hexavalent chromium.

         Use a safety pipet to transfer a 10 ml cooled sample, into a beaker, then dilute to approximately 100 ml; with CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER distilled or deionized water.

      2. Titrate with an N/2 solution of CoMat 01-030 SODIUM CARBONATE Na2CO3 to a permanent turbidity.

      3. ml of sodium carbonate solution x 5 = g/l of chromium trioxide

   5. Check for chloride content.

      1. Use a safety pipet to transfer a 50 ml cooled sample into a beaker, then dilute to approximately 300 ml with CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER.

      2. Add 20 ml of concentrated CoMat 01-058 NITRIC ACID HNO3 and 20 ml of a 1 percent solution of CoMat 01-059 SILVER NITRATE AgNO3, to the diluted sample.

      3. Heat to almost boiling point, then allow the precipitate to settle.

      4. When the sample upper liquid is clear, add a few drops of the silver nitrate solution to make sure that precipitation is completed.

      5. Cool, then let the mixture stand for 1 to 2 hours.

      6. Filter the sample through a sintered-glass crucible - (grade 4),using the Buchner flask and pump; to drain the solution through the filter.

      7. Wash the precipitate with a cold 1 percent solution of nitric acid, then with CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER and finally with CoMat 01-007 ETHYL ALCOHOL C2H5OH (DENATURED).

      8. Dry the precipitate at 221 deg F (105 deg C), then weigh as AgCl.

         1. g AgCl x 0.4079 = g NaCl.

         2. Therefore,

            1. (g AgCl x 0.4079 x 1000)/50 = g/l of NaCl, or:

            2. g AgCl x 8.2 = g/l of NaCl.

   6. Check for sulfate content - (That is, analyze for sulfuric acid).

      1. Use a pipet to transfer a 50 ml filtered sample into a 250 ml standard flask.

      2. Dilute with CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER to 250 ml, then shake well.

      3. Transfer 25 ml of the diluted solution into a beaker then further dilute, with distilled or deionized water, to approximately 150 ml.

      4. Add 20 ml of ethyl alcohol and 10 ml of concentrated CoMat 01-006 HYDROCHLORIC ACID.

      5. Boil-down to approximately 80 ml. Cool then dilute, with CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER, to approximately 150 ml.

      6. Bring to the boil, then add 15 ml of a 10 percent solution of CoMat 01-056 BARIUM CHLORIDE BaCl2x 2H2O; then continue boiling for 15 minutes.

      7. Allow the mixture to stand overnight, or for a similar period.

      8. Filter, by decantation, onto a CoMat 02-011 FILTER PAPER.

      9. Wash the precipitate with hot water, until all traces of the green chromium salts have disappeared.

      10. Dry, ignite, then weigh the precipitate as barium sulfate.

      11. Therefore, g/l of sulfuric acid = g of barium sulfate x 83.8.

2. SUBTASK 70-33-20-200-002 Control of the Dichromate Sealing Solution

   1. Control of solutions.

      1. The solution strength is maintained by analysis; followed by additions of CoMat 01-047 POTASSIUM DICHROMATE K2Cr2O7, of between 30 and 50 g/l.

      2. Control the pH level at between 5.6 and 6.0. Add CoMat 01-023 CHROMIUM TRIOXIDE CrO3(CHROM.ACID) to decrease the pH level and CoMat 01-030 SODIUM CARBONATE Na2CO3 to increase it.

   2. Analysis of the solutions.

      1. Use a pipet to transfer a 10 ml cooled sample, into a 100 ml standard flask.

      2. Dilute with CoMat 01-201 DISTILLED, DEIONIZED, DEMINERALIZED, OR REVERSE OSMOSIS (RO) WATER, then shake well.

      3. Use a pipet to transfer 10 ml of the diluted solution, into a beaker, then add 10 ml of a 50 percent solution of CoMat 01-043 SULFURIC ACID H2SO4.

      4. Use a buret to add 19.5 ml of an N/10 solution of CoMat 01-054 FERR.AMMON.SULPHATE FeSO42S04 6H2O then quickly titrate, with an N/10 solution of CoMat 01-055 POTASSIUM PERMANGANATE KMnO4, to a pink end-point.

         NOTE

         The total amount of potassium permanganate used, in the titration, is represented by T1; in the formula below.

      5. Add a further 0.5 ml of the N/10 solution of ferrous ammonium sulfate. Titrate with the N/10 solution of potassium permanganate, in drops, to a faint purple end-point.

      6. Carry-out a blank determination with each analysis:

         1. Pipet 10 ml of distilled or deionized water, into a beaker, then add 10 ml of the 50 percent sulfuric acid solution.

         2. NOTE

            The total amount of potassium permanganate used, in the titration, is represented by T2; in the formula below.

            Add 19.5 ml of the N/10 ferrous ammonium sulfate solution, from a buret, then quickly titrate with the N/10 potassium permanganate solution, in drops, to a faint purple end-point.

      7. Therefore, (T2 - T1) x 4.9 = g/l of potassium dichromate.