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pH value

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Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.tb.cub.t66910021
EISBN: 978-1-62708-250-1
... and alkalinity The pH defines the acidity or alkalinity of a solution. The pH is defined as −log(H + ); an increase of one pH unit is equivalent to an order of magnitude, or factor of 10, decrease in the hydrogen ion concentration. Figure 15 shows a pH scale ranging from 1 to 14. A value of pH 7 defines...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.t65940001
EISBN: 978-1-62708-302-7
... that the change in the Gibbs free energy is negative for these reactions at all values of pH, and hence, iron tends to corrode at all pH values. The rate of corrosion, however, depends on factors influencing the kinetic mechanisms of the several processes involved in the transport of ions from metal to solution...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.tb.cub.t66910049
EISBN: 978-1-62708-250-1
... (a) and (b) separates the oxidizing and reducing regions of the diagram. Fig. 5 Range of pH values for some common solutions Fig. 6 Approximate locations of several common environments on a potential-pH diagram Fig. 14 Methods of corrosion control for iron related...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2017
DOI: 10.31399/asm.tb.sccmpe2.t55090221
EISBN: 978-1-62708-266-2
... have very high pH values. Relatively little research has been performed in nonammoniacal environments. In the original milestone work performed by Mattsson ( Ref 7.9 ), the effect of pH on the SCC and film-forming characteristics of Cu-37Zn was studied in ammoniacal copper sulfate solutions, which...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 August 1999
DOI: 10.31399/asm.tb.caaa.t67870025
EISBN: 978-1-62708-299-0
... specimens exposed in water and in salt solutions at various pH values. Fig. 2 Pourbaix diagram for aluminum showing the conditions of corrosion, immunity, and passivation of aluminum at 25 °C (77 °F), assuming protection by a film of bayerite, Al 2 O 3 ·3H 2 O. Source: Ref 3 Fig. 3 Weight...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2015
DOI: 10.31399/asm.tb.cpi2.t55030005
EISBN: 978-1-62708-282-2
... − ) , which participate as the oxidizing agent in the cathodic corrosion reaction ( Eq 1 , 4 and Fig. 2 ). Due to the presence of H + ions, the moisture has a lower pH (often below 4.5). The addition of SO 2 air contamination, acid rain, results in a highly accelerated corrosion rate. Some metals...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2015
DOI: 10.31399/asm.tb.cpi2.t55030209
EISBN: 978-1-62708-282-2
... dependent on the acids present and the hydrogen sulfide concentration. At pH value near neutral (7.0), corrosion due to hydrogen ions is reduced but corrosion due to bisulfide from the ionization of hydrogen sulfide increases. Copper alloys, such as admiralty brass and Monel, become susceptible to corrosion...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2017
DOI: 10.31399/asm.tb.sccmpe2.t55090043
EISBN: 978-1-62708-266-2
... effects on SCC. When more negative potentials, lower pH values, and lower temperatures promote SCC, a hydrogen-embrittlement mechanism is generally thought to be active. The reverse trends are often believed to indicate an active-path mechanism. However, some research has suggested that SCC under both...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2008
DOI: 10.31399/asm.tb.ssde.t52310011
EISBN: 978-1-62708-286-0
... large region that is of relevance to pH values in water solutions. Since Cr 2 O 3 is protective, it prevents further corrosion. When chromium is added to iron as an alloying element, it corrodes selectively due to its low reduction potential, but this means that it also protects the iron alloy due...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.9781627083027
EISBN: 978-1-62708-302-7
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.t65940271
EISBN: 978-1-62708-302-7
..., the films may become thermodynamically unstable at very high and/or low pH values, leading to high uniform corrosion rates ( Ref 7 ). These films relate to the bulk oxide (e.g., Al 2 O 3 ) but tend to be amorphous; they also exhibit very high resistance to electron conduction. This behavior is in contrast...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2000
DOI: 10.31399/asm.tb.cub.t66910193
EISBN: 978-1-62708-250-1
...; to strong alkalis, represented by sodium hydroxide and calcium hydroxide at pH 14. Fig. 1 The pH of several common environments The measured pH of several common acids and alkalis are as follows: Hydrochloric acid and sulfuric acid are strong acids and have low pH values. Boric acid...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 June 2007
DOI: 10.31399/asm.tb.pmsspmp.t52000101
EISBN: 978-1-62708-312-6
... , chromium addition to iron extends the passive region of iron to lower pH values for intermediate values of E ; the addition of nickel further extends the regions of immunity and passivation. Osozawa and Engell ( Ref 3 ) show such relationships for various chrome-nickel steels. In section 5.2.4...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2009
DOI: 10.31399/asm.tb.bcp.t52230107
EISBN: 978-1-62708-298-3
... (such as would be present in airborne dust samples) are effectively sequestered with EDTA. Iron, which is not complexed by EDTA at the high pH values used in the Morin method, is sequestered by citric acid and triethanolamine. It should be noted that the purity of the Morin reagent is of importance; even...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.t65940183
EISBN: 978-1-62708-302-7
... are extrapolations of lines 13 and 17. Based on Ref 2 Fig. 5.4 Representative polarization curve for iron in buffered solution of pH = 7. Dashed curve extends to the half-cell potential of iron with a Fe 2+ = 10 –6 . Letters along curves relate to reactions (details can be found in the text...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2017
DOI: 10.31399/asm.tb.sccmpe2.t55090241
EISBN: 978-1-62708-266-2
... range is further illustrated in Fig. 8.2 , which gives results of weight loss measurements for alloy 3004-H14 specimens exposed in water and in salt solutions at various pH values. Fig. 8.1 Pourbaix diagram for aluminum with an Al 2 O 3 · 3H 2 O film at 25 °C (75 °F). Potential values...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 January 2017
DOI: 10.31399/asm.tb.sccmpe2.t55090067
EISBN: 978-1-62708-266-2
... ), it is possible for this cathodic reaction to occur: H 2 O → OH − + ½ H 2 − e − Fig. 3.3 Values of potential and pH at the crack tips of several steels during stress-corrosion crack propagation. Source: Ref 3.6 Fig. 3.4 Effects of anodic and cathodic...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 December 2015
DOI: 10.31399/asm.tb.cpi2.t55030089
EISBN: 978-1-62708-282-2
...% of the total corrosion current; pH values substantially above this level would be needed to suppress the effect completely. Furthermore, if such treatments may be useful to control preferential HAZ corrosion when it has not been anticipated, it is considered to be more reliable to avoid the problem through...
Series: ASM Technical Books
Publisher: ASM International
Published: 01 July 2000
DOI: 10.31399/asm.tb.fec.t65940127
EISBN: 978-1-62708-302-7
... of different cathodic areas, A c , and a constant anodic area, A a Fig. 4.16 Estimation of E corr and I corr for iron at the indicated values of pH. Curves for hydrogen-ion reduction are based on experimental values of the polarization parameters governing the polarization curves. The anodic...
Book Chapter

Series: ASM Technical Books
Publisher: ASM International
Published: 01 October 2011
DOI: 10.31399/asm.tb.mnm2.t53060369
EISBN: 978-1-62708-261-7
...), passivity, and immunity. In the region of potentials and pH values defined by Fe(OH) 3 and Fe 2 O 3 (the solid compounds thermodynamically stable in these conditions), the initial corrosion process forms a very dense and usually thin and impervious rust layer of iron oxide and oxyhydroxides that acts...