ISO /DIS 8407 DRAFT IN TERN ATION AL STAN DARD
ISO/ DIS
84 07
Metals
and
alloys
—
Procedures
for
removal
of
corrosion products from corrosion test specimens
1 S c o p e a n d fi e l d o f a p p l i c a t i o n 1 . 1 T h i s I n t e r n a t i o n a l S t a n d a r d s p e c i fi e s for the procedures for the removal of corrosion products formed on metal and alloy corrosion test specimens during t h e i r ex p o s u r e i n c o r r o s i v e e n v i r o n m e n t s . 1 . 2 T h e p r o c e d u r e s s p e c i fi e d a r e d e s i g n e d to remove corrosion products without s i g n i fi c a n t r e m o v a l o f b a s e m e t a l . T h i s allows an accurate determination of the mass Ioss of the metal or alloy which o c c u r r e d d u r i n g ex p o s u r e t o t h e c o r r o s i v e environment. 1.3 These procedures, in some cases, may apply to metal coatings. However, p o s s i b l e e ff e c t s f r o m t h e s u b s t r a t e m u s t be considered. 2 Procedures 2.1 Corrosion product removal procedures can be divided into three general categories: chemical, electrolytic and mechanical. 2.1.1 An ideal procedure should remove o n l y c o r r o s i o n p ro d u c t s a n d n o t r e s u l t i n removal of any base metal. To determinate the mass loss of the base metal when removing corrosion products, replicate uncorroded control specimens should be cleaned by the same procedure as used on the test specimen. By weighing the control specimen before and a ft e r c l e a n i n g ( w e i g h i n g t o t h e fi ft h s i g n i fi c a n t fi g u r e is suggested), the ex t e n t of metal loss resulting from cleaning can be utilized to correct the corrosion mass loss.
2.1.2 The procedure given in 2.1.1 may not be reliable for cases where heavily corroded specimens are to be cleaned. The application of replicate cleaning procedures to specimens with corroded s u r f a c e s w i l l o ft e n , e v e n i n t h e a b s e n c e o f corrosion products, result in continuing
mass losses. This is because a corroded surface, particularly of a multiphase alloy, is o ft e n more susceptible that, a new machined or polished surface to corrosion by the cleaning procedure. In such cases, the following method of determining the mass loss due to the cleaning procedure is preferred. 2.1.2.1 The cleaning procedure should be repeated on specimens several times. The mass loss should be d e t e r m i n e d a ft e r e a c h c l e a n i n g b y w e i g h i n g t h e s p e c i m e n ( t o t h e fi ft h s i g n i fi c a n t fi g u r e i s s u g g e s t e d ) . 2.1.2.2 The mass Ioss should be showed or a graph as a function of the number of equal cleaning cycles (see t h e fi g u r e ) . Tw o l i n e s w i l l b e o b t a i n e d AB and BC. The latter will correspond t o c o r r o s i o n o f t h e m e t a l a ft e r r e m o v a l of corrosion product. The true mass loss due to corrosion will correspond to the point D obtained by ex t r a p o l a t i o n t o z e r o t i m e o f t h e l i n e BC. When the cleaning method does not corrode the metal, the line BC will be horizontal and the true mass loss will be that represented by point B since D will have the value of B. 2.1.2.3 To minimize uncertainty associated with corrosion of the metal by the cleaning method, a method should be chosen to provide the lowest slope (near to the horizontal) of line BC. 2 . 1 . 3 Re p e a t e d t h e t r e a t m e n t m a y b e required for complete removal of corrosion products. 2.1.2.1. 2.1.4 All prepared
cleaning solutions shall be with distilled water and
reagent grade chemicals. 2.1.5 Any cleaning procedure should be followed by a thorough rinsing of
1) W henever distilled water is required in this specif ication, deionized water with a conductivity less than 20 µSiemens/cm may be used
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ISO /DIS 8407 the test specimen with distilled water and immediate drying. 2 . 2 C h e m i c a l p r o c e d u r e o n l y ex p o s u r e o f t h e c o r r o s i o n t e s t s p e c i m e n i n a s p e c i fi c chemical solution which is designed to remove
the
corrosion
products
with
minimal dissolution of any base metal. Several procedures are listed in the a n n ex . WA R N I N G — t h e s e m e t h o d s m a y b e hazardous to personnel. They should n o t b e c a r r i e d o u t b y i n ex p e r i e n c e d employees or without professional supervision.
2.2.1 Chemical cleaning is often preceded by light brushing of the test specimen to remove loose, bulky corrosion products.
method is recommended. The mechanical forces used to cleaning should be held as nearly constant as possible.
2.2.2 Intermittent removal of specimens from the chemical solution for light brushing can often facilitate the removal of tightly adherent corrosion products. 2.2.3 Chemical cleaning also is often followed by light brushing to remove loose products.
3 Test report Reports of results shell include the following information: a) Reference to this International Standard;
2.3 Electrolytic cleaning also can be utilized for removal of corrosion products. Several useful methods for corrosion test specimens of iron, cast iron or steel are given in the annex. Electrolytic cleaning should be preceded by brushing of the test specimen to remove loose, bulky corrosion products. Brushing also should follow the electrolytic clearing to remove any loose slime or deposits. This will help to minimize any redeposition of metal from reducible corrosion products which would reduce the apparent mass loss. 2.4 Mechanical procedures can include scraping, scrubbing, brushing, ultrasonic methods, mechanical shock, and impact blasting (grit blasting. water-jet blasting, etc.) These methods are often utilized to remove heavily encrusted corrosion products. Scrubbing with a bristle brush and mild abrasive/distilled water slurry can also be used to remove corrosion products. Vigorous mechanical cleaning will result to the removal of some base metal, so care should be exercised. These methods should be used only when others fail to provide adequate removal of corrosion products. As with, other methods, correction for metal boss doe to the cleaning
b) The procedure utilized in the removal of corrosion products following corrosion testing; c) For chemical procedures, the composition and concentrations of chemicals employed, the solution temperature and duration of cleaning; d) For electrolytic procedures, the composition and concentrations of chemicals employed the solution temperature, the anode material and current density, and duration of cleaning; e) For mechanical procedures, the specific mechanical method (bristle brush scrubbing, wooden scraper, etc.) employed, any abrasive compounds utilized, and duration of cleaning;
f) Where multiple procedures are used, the appropriate details for each method and the sequence of methods;
g) The results from cleaning of controls (see 2.1.1) or from repetitive cleaning steps (see 2.1.2) designed to assess mass loss from removal of base metal during to cleaning process.
Mass loss
C B
D
A
Number of clearing cycles
2
ISO /DIS 8407 Figure
—
Mass loss of corroded specimens resulting from repetitive cleaning cycles
Annex Chemical and electrolytic cleaning procedures for removal of corrosion products (This annex does not form part of the standard.)
A.0 Introduction In the development of this international Standard, a number of sources were consulted to identify chemical and electrolytic cleaning procedures. This annex summarizes the results of this survey.
A.1 Procedure Tables 1 and 2 summarize various chemical and electrolytic cleaning procedures for removal of corrosion products. The specific choice of procedure for a given material will depend on many factors including previous experience. This international Standard should be consulted for guidance in the proper application of the procedure in tables 1 and 2. For all the cleaning procedures listed, it la suggested that surfaces to be cleaned of corrosion products be maintained vertical. This will minimize retention of any gases released during the cleaning procedure at horizontal surfaces which in turn may alter the uniformity of the cleaning process.
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ISO /DIS 8407
Table 1 — Chemical cleaning procedures for removal of corrosion products
Designati on
C.1.1
Material Aluminium and aluminium alloys
Chemical 50 ml phosphoric acid (H3P04, ρ= 1,69 g/ml) 20 g chromium trioxide (CrO3) Distilled water to make 1000 ml
Time
Temperature
5 to 10 min
90ºC Boiling
1 to 5 min
20 to 25ºC
1 to 3 min
20 to 25ºC
1 to 3 min
20 to 25ºC
1 to 3 min
20 to 25ºC
5 to 10 sec
20 to 25ºC
30 to 60min
40 to 50ºC
1 to 25 min
20 to 25ºC
Nitric acid (HN03, 1,42 g/ml ) C.1.2
C.2.1
Copper and copper alloys
C.2.2
C.2.3
C.2.4
C.2.5
c.3.1
Iron and steel
C.3.2
500 ml hydrochloric acid (HCI, ρ= 1,19 g/ml) Distilled water to make 1 000 ml 4,9 g sodium Cyanide (NaCN) Distilled water to make 1000 ml 100 ml sulfuric acid (H2 SO4, ρ =1,84 g/ml) Distilled water to make 1000 ml 120 ml sulfuric acid (H2S04, ρ= 1,84g/ml) 30 g sodium dichromate (Na2Cr2O7.2H20) Distilled water to make 1000 ml 54 ml sulfuric acid (H2S04, ρ= 1,84g/ml) Distilled water to make 1000 ml 1000 ml hydrochloric acid (HCI, ρ= 1,19 g/ml) 20 g antimony trioxide (Sb2O3) 50g stannous chloride (SnCl2) 50g sodium hidroxide (NaOH) 200 g granulated zinc or zinc chips Distilled water to make 1000 ml 200g sodium hidroxide 20 g granulated zinc or zinc chips Distilled water to make 1000 ml
C.3.3
C.3.4
200 g diammonium citrate[(NH4)2HC6H5O7] Distilled water to make 1000 ml
C.3.5
500 ml hydrochloric acid (HCI, ρ= 1,19 g/ml) 3.5 g hexamethylene tetramine Distilled water to make 1000 ml
C.4.1
C.4.2
C.4.3
Lead and lead alloys
10 ml acetic acid (CH3COOH) Distilled water to make 1000 ml 50 g ammonium acetate (CH3COONH4) Distilled water to make 1000 ml 250 g ammonium acetate (CH3COONH4) Distilled water to make 1000 ml
30 to 40 min
80 to 90ºC
30 to 40 min
80 to 90ºC
20 min
75 to 90ºC
10 min
20 to 25ºC
5 min
Boiling
10 min
60 to 70 ºC
5 min
60 to 70 ºC
Remarks
If corrosion product films remain, then follow with nitric acid procedure below.
Remove extraneous deposits and bulky corrosion products to avoid reactions that may result in excessive removal of base metal. De- aeration of solution with purified nitrogen will minimize base metal removal. Remove copper sulfide corrosion products which may not be removed by above hydrochloric acid treatment. Remove bulky corrosion products before treatment to minimize copper redeposition on specimen surface.
Removes redeposited copper resulting from sulfuric acid treatment. De – aerate solution with nitrogen. Brushing of test specimens to remove corrosion products followed by reinmersion for 3 to 4 sec is recommended. Solution should be vigorously stirred or specimen should be brushed. Longer times may be required in certain instances. Caution should be excercised in the used of any zinc dust since spontaneous ignition upon exposure to air can occur.
Caution should be excercised in the used of any zinc dust since spontaneous ignition upon exposure to air can occur.
Longer times may be required in certain instances.
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ISO /DIS 8407
Table 1 — (Continued)
Designation
C.5.1
Material Magnesium and Magnesium alloys
Chemical 100 g ml Chromiun trioxide (CrO3) 10 g silver nitrate(AgNO3) Distilled water to make 1000 ml
Time
Temperature
1 min
Boiling
1 min
20 to 25ºC
1 to 3 min
20 to 25ºC
1 to 3 min
20 to 25ºC
20 min
60ºC
10 to 60 min
70 ºC
5 min
60 ºC
5 min
Boiling
5 to 20 min
20 to 25ºC
20 min
Boiling
10 min
Boiling
Remarks
The silver salt is present to precipitate chloride.
200 g Chromiun trioxide (CrO3) 10 g silver nitrate(AgNO3) C.5.2
20 g barium nitrate [Ba(NO3)2] Distilled water to make 1000 ml Nickel and Nickel alloys
C.6.1
C.7.1
Stainless steels
C. 7.2
100 g citric acid (C6H8O7) 50 ml sulfuric acid (H2S04, ρ= 1,84g/ml) 2 g inhibitor (diorthotoly thlourea or quinoline ethyliodide or βnaphtholquinoline) Distilled water to make 1000 ml
C. 7.3
200 g sodium hydroxide (Na OH)30 g potassium permanganate (KMnO4) 100 g diammonium citrate [(HN4)2HC6H5O7] Distilled water to make 1000 ml
C. 7.4
100 ml nitric acid (HNO3, ρ= 1,19 g/ml) 20 ml hydrofluoric acid (HF, ρ= 0,987 g/ml) Distilled water to make 1000 ml
C. 7.5
200g hydroxide sodium (NaOH) 50 g zinc powder Distilled water to make 1000 ml
C.7.6
C.8.1
150 ml hydrochloric acid (HCI, ρ= 1,19 g/ml) Distilled water to make 1000 ml 100 ml sulfuric acid (H2 SO4, ρ =1,84 g/ml) Distilled water to make 1000 ml 100 ml nitric acid (HNO3, ρ= 1,42 g/ml) Distilled water to make 1000 ml 150g diamonium citrate [(HN4)2HC6H5O7] Distilled water to make 1000 ml
Tin and Tin alloys
150 g trisodium phosphate (Na3PO4.12H2O) Distilled water to make 1000 ml
The barium salt is present to precipitate sulfate.
Caution should be excercised in the used of any zinc dust since spontaneous ignition upon exposure to air can occur.
C.8.2
5
ISO /DIS 8407 50 ml hydrochloric acid (HCl, ρ=1.19 g/ml) Distilled water to make 1000 ml
C. 9.1
Zinc and Zincs Alloys
150 ml ammonium hydroxide (NH4OH), ρ=0.90 g/ml) Distilled water to make 1000 ml Followed by 50 g Chromiun trioxide (CrO3) 10 g silver nitrate(AgNO3) Distilled water to make 1000 ml
10 min
20 ºC
5 min
20 to 25ºC
15 to 20 sec
Boiling
The silver nitrate should be dissolved in water and added to the boiling chromic acid to prevent excessive crystallization of silver chromate. The chromic acid must be sulfate – free to avoid attack of zinc base metal.
Table 1 (concluded) Designation
Material
C.9.2
C.9.3
Chemical 100 g ammonium chloride (NH4Cl) Distilled water to make 1000 ml 200 g Chromiun trioxide (CrO3) Distilled water to make 1000 ml
Time
Temperature
2 to 5 min
70 °C
1 min
80 °C
15 sec
20 to 25 °C
5 min
20 to 25 °C
2 to 5 min
70 °C
C.9.4 85 ml hydriolic acid (Hl, ρ= 1.5 g/ml) Distilled water to make 1000 ml 100 g ammonium acetate [(HN4)2S2O8] Distilled water to make 1000 ml 100 g ammonium acetate [CHOONH4] Distilled water to make 1000 ml
C.9.5 C.9.6
Remarks
Chloride contamination of the chromic acid from corrosion products formed in salt environments should be avoided to prevent attack of the zinc base metal. Some zinc base metal may be removed. A control specimen (see 2.1.1.) should be employed. Particularly recommended for galvanized steel.
Table 2 – Electrolityc cleaning procedures form removal of corrosion products Designation E.1.1
Material Iron, Cast Iron, steel.
Chemical 75 g sodium hidroxide (NaOH) 25 g sodium sulfate(Na2SO4) 75 g sodium carbonate(Na2SO4) 75 g sodium carbonate( Na2CO3) Distilled water to make 1000 ml
Time
Temperature
Remarks
20 to 30 min
20 to 25 °C
Cathodic Treatment with 100 to 200 A/m2 current density. Use carbon, platinum or stainless steel anode.
3 min
75 °C
Cathodic Treatment with 2000 A/m2 current density. Use carbon, platinum or lead anode.
5 min
20 to 25 °C
3 min
75 °C
E.1.2 28 ml sulfuric acid (H2SO4, ρ= 1.84 g/ml) 0.5 g inhibitor(diorthotoly thlourea or quinoline ethyliodide or βnaphtholquinoline) Distilled water to make 1000 ml
E.1.3
100 g diammonium citrate {(NH4)2HC6H5O7)} Distilled water to make 1000 ml
E.2.1
Lea and lead alloys
28 ml sulfuric acid (H2SO4, ρ= 1.84 g/ml) 0.5 g inhibitor(diorthotoly thlourea or quinoline ethyliodide or βnaphtholquinoline)
Cathodic Treatment with 100 A/m2 current density. Use carbon or platinum anode. Cathodic Treatment with 2000 A/m2 current density. Use carbon, platinum or lead anode.
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ISO /DIS 8407 Distilled water to make 1000 ml
E.3.1
E.4.1
E.4.2
Copper and copper alloys
Zinc and cadmium
7.5 g potasium chloride (KCl) Distilled water to make 1000 ml 50 g sodium hydrogenphosfhate (Na2HPO4) Distilled water to make 1000 ml 100 g sodium hydroxide (NaOH) Distilled water to make 1000 ml
1 to 3 min
20 to 25 °C Cathodic Treatment with 100 A/m2 current density. Use carbon or platinum anode.
5 min
70 °C
1 to 2 min
20 to 25 °C
Cathodic Treatment with 110 A/m2 current density. Specimen shall be energized prior to inmersion. Use carbon, platinum or stainless steal anode. Cathodic Treatment with 100 A/m2 current density. Specimen shall be energized prior to inmersion. Use carbon, platinum or stainless steal anode.
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