FERROXYL TEST FOR IRON CONTAMINATION

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Alan Norris
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1 FERROXYL TEST FOR IRON CONTAMINATION 1. SCOPE This specification describes a highly sensitive test for detecting free iron on surfaces of equipment, and the preparation of the equipment for the test. 2. SAFETY PRECAUTIONS FOR DU PONT EMPLOYEES MAKING INSPECTIONS IN SUPPLIERS' SHOPS 2.1 Acid-cleaning and ferroxyl solutions must be handled carefully and the following precautions observed Safely goggles of the chemical type are to be worn when spraying, mixing, or pouring acid or ferroxyl solution Solution must be kept form contact with the skin. Should contact occur unavoidably, the skin must be washed immediately with water Hands are to be protected with rubber gloves If the solution is applied by spray gun in an enclosure, adequate protective rubberized clothing shall be provided Employees should not breathe vapors of ferroxyl solution and adequate protection always shall be provided when testing in a closely confined place. This is to include masks supplied with air from an outside source that has been filtered by an apparatus similar to the Purolator when such is available. If this filtering equipment is not available, a self-contained air mask is required like the Scott Air Pak or the Mine Safety Appliance Company's Chem-Ox. Fit testing of respirators is an

2 essential part of any protection program. 3. SAFETY PRECAUTIONS IN DU PONT PLANTS 3.1 When this specification is employed on Du Pont plants or construction sites, the local safety rules shall govern in cases of conflict with this specification. 3.2 Both nitric and hydrofluoric acids emit highly toxic fumes when heated to decomposition. The following is recommended Avoid welding when possible after ferroxyl testing In the event that welding becomes necessary after ferroxyl testing, all traces of the ferroxyl solution must be completely removed Adequate ventilation must be provided. This is especially important when welding in enclosed areas, such as vessels, etc. 4. GENERAL 4.1 Ferroxyl testing is effective for the following materials: All AISI 200, 300, and 400 series All Alloy 20 type material Ni-Mo-Cr Alloy C-276 and C-4 Inconel and Incoloy Precipitation hardening stainless steels High-carbon, high-chromium(12% chromium) tool steels Nichrome Titanium Chromium plating Aluminum 4.2 Whenever this test is required, it shall be specified in the purchase order.

3 Fabricators of equipment shall indicate the items in the Bill of Material submitted to Du Pont which are subject to such tests after fabrication. 4.3 Provisions are given for two levels of freedom from iron Percent Free. This shall be specified in the purchase order when equipment must be absolutely devoid of all free iron. The test will be applied to 100 percent of the surface which must be free from any indication of iron Less Than 100 Percent Free. This shall be specified in the purchase order when a slight amount of iron contamination can be tolerated. The Du Pont engineer is to consult with the Du Pont materials engineer to develop criteria for test. 4.4 The Du Pont inspector responsible shall witness the test. 5. SURFACE PREPARATION AND PROTECTION 5.1 Prior to ferroxyl tests, the equipment shall be thoroughly cleaned of foreign material. 5.2 The following procedures will help fabricators produce equipment which will meet the requirements of this specification When closure of equipment is done by welding from one side only, as in the case of butt or lap welds, the internal seams must be scal welded. Further, all internal welded parts must be seal welded. Where fabrication conditions make seal welding impossible, the fabricator must submit to Du Pont, in writing, a welding and cleaning procedure for approval with quotation Weld surface must be as clean as the adjacent plate surfaces. All spatter and slag must be removed, and cracks or porosity eliminated in advance of cleaning for ferroxyl tests If wire brushes, steel wool, or similar agents are to be used in conditioning surfaces, only such articles as were produced from Type 300 series stainless steel, and

4 are uncontaminated, shall be employed Grinding operations should be done only with aluminum oxide wheels that have not been previously employed on carbon steels Wherever possible, stainless steel tools or accessories should be employed. Carbon steel tools should be protected adequately from direct contact with the surfaces to be later subjected to the ferroxyl test. This may be done with rubber, stainless steel, or tape Forming rolls and dies should be inspected for undesirable projections that must be dressed down before use. Contamination possibilities during forming operations may be prevented, to a large extent, if paper or cardboard interlays are arranged between the material and the rolls or dies. Shearing and forming brake tables should be covered with paper to minimize the chance of contact between the carbon steel surfaces and the fabricated material Clean rubber overshoes should be worn by workmen walking on equipment surfaces or entering such equipment or tanks. Such overshoes should be used as little as possible except for the purpose stated, and should be washed off frequently with a pickling solution to preserve their cleanliness Dust that could contain free iron should be removed from the fabricated parts as construction proceeds Castings should be molded in new sand restricted to this use, and neither chaplets nor chill pins made of carbon steel are to be employed. Castings should be steam cleaned and thoroughly rinsed with water after pickling All hydrostatic tests should be performed before preparing the surfaces for ferroxyl testing A thorough detergent wash or steam cleaning followed by rinsing is normally required on all surfaces prior to ferroxyl testing to assure freedom from iron contamination.

5 5.3 If contamination is shown by test after such cleaning, use one of the following methods for additional cleaning Degreasing. Greasy surfaces may contain free iron which remain after the detergent wash. Degreasing is suggested to be followed by another detergent wash and rinse If contamination appears to be the result of abrasive residues left by carbon steel implements on the surfaces of the Type 300 or 400 series, or Alloy 20 Cb-3 materials, the cleaning method employed to remove such contamination will depend upon the composition and heat-treatment condition of the particular item Mill products or castings of any of the above compositions which are in the solution-annealed condition or weldments of Types 304L, 316L, 321, 347, and No.20 Cb-3 may be cleaned by scrubbing with, or immersing in, a pickling solution composed of: 10 percent by volume of percent nitric acid; 1.3 percent by volume of 52 percent hydrofluoric acid; balance water Under no conditions shall the pickling solution be allowed to contact the parts for more than 30minutes at room temperature, or 15minutes at temperatures up to 150 (66 ) Weldments of Types 304, 316, or any of the other non-elg, nonstabilized grades or severely sensitized items(such as those which have been stress relieved) of any of the grades(including ELC and stabilized) shall not be cleaned in HNO₃-HF solutions. Suggested cleaning methods include blasting with previously unused, ironfree sand or aluminum grit, and cleaning with milder acids such as 30 percent by weight HNO₃at 150 (66 ) max or 10 percent by weight oxalic at 150 (66 ) max, for a period not to exceed 15minutes The type 400 series stainless steels after pickling will contain a gray smudge. This smudge must be removed by thorough washing using water, detergent, and scrub brushes prior to ferroxyl testing. If this smudge in not completely removed, the ferroxyl test will give a positive indication. Note: The hardenable Type 400 series and the precipitation-hardened stainless steels in the hardened condition are subject to hydrogen embrittlement. Whenever possible, cleaning of these materials should be by mechanical methods. Plain nitric acid solution

6 or citric acid-sodium nitrate mixture is much less prone to cause hydrogen embrittlement than nitric-hydrofluoric acid solution. If acid must be used, the parts should be heated from 250 to 300 (121 to 149 ) and held for 24hours after pickling Information concerning suitable pickling solution and procedures for the other materials listed in 4.1 may be obtained from the suppliers of these materials If contamination is still present after pickling, sandblasting is suggested, using sharp, clean, iron-free sand. Sand should not be reused and should come from hoppers that were thoroughly cleaned before filling. Sandblasting of clad material should not be carried to the point of seriously reducing the cladding thickness. Any other blasting materials such as aluminum grit shall not have been used previously on carbon steels. 6. TESTING AND INTERPRETATION OF RESULTS 6.1 Testing Solution Distilled water 94% by wt 1000cc 1gal Potassium 3% by wt 30g 4 ox ferricyanide Nitric acid (60-67 ) 3% by wt 20cc 1/5 pt Because this solution will begin to discolor after mixing, it shall only be prepared immediately prior to use. 6.2 Application of Solution and Interpretation of Results Apply the solution with a spray atomizer made of plastic, rubber, glass, or aluminum. Be certain that the atomizer contains no iron parts. The presence of iron will be indicated by the solution turning to a dark blue color. If dark blue areas develop within 30seconds after the solution has wetted the surface, the test is considered positive and the contaminated areas must be cleaned and retested. Unless otherwise stated, it is required that 100 percent of the area show a negative reaction in this test.

7 In either case, wash immediately to prevent blue stains from appearing on the surface. Caution: Dark areas may appear after 30seconds and these results may be misinterpreted Small parts may be tested by immersing in the solution. It the solution becomes contaminated, it must be replaced. The solution must be washed from the parts immediately after testing During ferroxyl testing, the solution is to be washed from the surfaces with water as soon after the 30-second interval as possible. If water does not remove the stain on the surface, a 10 to 20 percent solution of acetic acid or water-white vinegar can be used, applied by a scrubbing action. CP ammonium hydroxide also may be used for this purpose Waste Disposal Method. Disposal of in accordance with local, state, and federal regulations Wipe surfaces dry with a clean white cloth after rinsing. 7. TUBULAR HEAT EXCHANGERS 7.1 When the ferroxyl test is to be applied, the order or drawings will specify whether the tube side, shell side, or both, are to be tested. The test is to be made as with any other equipment with the following exceptions Tube Side. The face of the tubesheet is to be tested in the usual manner. The insides of the tubes are to be tested by inserting a swab saturated with the solution to a distance extending approximately 1 inch beyond the roller area and then withdrawn. If the characteristic blue color appears on the swab, indicating iron contamination, the tube is to be recleaned and retested until the test is negative Shell Side. The solution is to be sprayed on the outside of the tubes and examination made as outlined in section 6. If, within 30seconds, any areas visible from

8 the outside of the bundle show iron contamination, those areas are to be recleaned and retested until the test is negative Wipe surfaces dry with a clean white cloth after rinsing. 8. PREPARATION FOR SHIPMENT OR STORAGE 8.1 Immediately after the test, the equipment is to be dried and closed to avoid contamination and damage during handling, shipping, and storage Small openings are to be sealed by completely covering with an adhesive tape and this, in turn, protected by metal or waterproof plywood covers held in place with bolts or steel banding Large openings, such as manholes, are to be covered with full iron-free gasket disks and metal or waterproof plywood covers. The covers are to be completely sealed with adhesive tape covering the flange and edges. Four or more bolts are to be employed Large openings, such as the open ends of columns or open-top bins, are to be closed by special methods. The proposed closure is to be briefly described in the quotation. This is to be in the form of a sketch showing the arrangement and materials to be used Small parts are to be packed in clean paper and boxes for protection. 8.2 Prior to shipment, the Du Pont inspector is to witness and approve the closure of all ferroxyl tested equipment. 8.3 The closures or seals provided by the vendor are not to be disturbed or removed until the adjoining equipment(pipe, agitator, instrument, etc) is to be physically connected in the field. Care must be exercised to prevent the entry of any foreign material, especially rust of other products of corrosion which may be in the vicinity.

9 9. SPECIAL MARKING 9.1 Any marking paint, inks, etc, used for purpose of identification shall not contain harmful quantities of low-melting metals or metal salts such as zinc, lead, or cadmium which can cause cracking during welding or heating, or of chlorides which can cause stress-corrosion cracking. Refer to SP3D or a materials engineer to ensure suitability of marking materials. 9.2 In addition to the marking required by other applicable specifications, equipment(such as tanks) which has been tested and can be closed shall have the statement "FERROXYL TESTED - DO NOT REMOVE SEALS" painted on the outside in a conspicuous place in letters at least 6 inches high, where practical. Parts which are crated or boxed shall have the crate or box similarly marked. Other parts which are shipped loose shall be tagged, the tag being marked as above.

Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts 1

Designation: A 967 01 e1 Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts 1 This standard is issued under the fixed designation A 967; the number immediately following