Historical Use of Chlorinated Solvents and Their Stabilizing Compounds - Environmental Investigation and Remediation - page 37

TABLE 1.18
Average Metal Corrosion Rates of Chlorinated Solvents

Corrosion Rate a (mils/year) b

Solvent Metal Inhibitor 2024 Aluminum 1010 Iron Zinc

Dichloromethane, technical grade No

<1 <1 <0.1

Methyl chloroform Yes

<3 <1 <1

Trichloroethylene with antioxidant No

<0.1 <0.1 <0.1

Perchloroethylene with antioxidant No

<0.1 <0.1 <1

Source: Archer, W.L. and Stevens, V.L., 1977, Industrial & Engineering Chemistry, Product Research and Development
16(4): 319-326.
a Penetration per year, determined in seven-day rel ux tests.
b 1 mil

= 0.001 in. = 0.0254 mm.

The direct reaction between a chlorinated solvent, such as methyl chloroform, and a metal, such
as aluminum, iron, or zinc, produces the metal chloride and the saturated dimer of the chlorinated
reactant (Archer, 1984):

2Al + 6CH 3 CCl 3 3CH 3 CCl 2 CCl 2 CH 3 + 2AlCl 3
Dimerization
Methyl chloroform

(1.12)

The saturated dimer can in turn react with the metal to give the unsaturated cis and trans dimers,
CH 3 CCl CClCH 3 .

Reactions of stabilized and unstabilized solvents with various metal alloys have been the subject
of extensive study. Numerous patents describe the rapid devolution of methyl chloroform rel uxed
with aluminum, which proceeds to a black tarry mass in as little as 20 min. The presence of a sepa-
rate water phase l oating atop the solvent accelerates the rate of metal corrosion for all solvents
(Archer, 1984). Results of additional rel ux (boiling and condensing solvent) and high-temperature
exposure corrosion tests are listed in Tables 1.18 and 1.19.

=

TABLE 1.19
Metals Corroded by Trichloroethylene and Dichloromethane at More Than 50 mils
Penetration per Year
Solvent Metal Temperature (°C)

Trichloroethylene Austenitic Cr-Ni stainless steel (18-8; 304/304L/347)

Lead

80-107
−4-24

Mo superalloy (Ni-Cr-Fe-9Mo; 625/725) 107-135

Mo superalloy (Ni-16Cr-16Mo; C276) 107-135

Mo superalloy (Ni-20Cr-16Mo-4W; 686) 107-135

Mo superalloy (Ni-22Cr-16Mo; C22/59) 107-135

Mo superalloy (Ni-23Cr-16Mo-1Cu; C20000) 107-135

Nickel (200) 107-135

Nickel-copper (400) 107-135

Steels, carbon/low alloy 80-107

Dichloromethane Austenitic Cr-Ni stainless steel (18-8; 304/304L/347) 88-139

Source: NACE International, The Corrosion Society, 2002, Corrosion survey database (COR . SUR). http://www.knovel.
com/knovel2/Toc.jsp?BookID=532&VerticalID=0 (accessed 2006).
Note: 1 mil = 0.001 in. = 0.0254 mm.