Novel sulfonium corrosion inhibitors in aqueous acid solutions
AssigneeThe Dow Chemical Company
InventorsWilliam J. Settineri, Wayne W. Frenier, James H. Oswald
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Abstract
The corrosion of metal surfaces in contact with aqueous acid cleaning solutions is inhibited by sulfonium salt corresponding to the formula ##STR1## wherein n is 1 or 2; R.sub.1 is an electron withdrawing group; R.sub.2 is a hydrocarbyl radical or inertly-substituted hydrocarbyl radical of up to about 24 carbon atoms; R.sub.3 is alkyl of from 1 to 4 carbon atoms, inertly-substituted alkyl of 2-4 carbon atoms, allyl, phenyl or inertly-substituted phenyl; or R.sub.2 and R.sub.3 are joined to form a 5- or 6-membered heterocyclic ring; and A.sup.- is a compatible anion. These sulfonium salts are effective corrosion inhibitors even in the presence of ferric ions.
Claims16
An aqueous acidic cleaning solution of at least one nonoxidizing inorganic acid or organic acid or mixtures thereof having dissolved or dispersed therein at least one sulfonium salt corresponding to the formula ##STR5## wherein n is 1 or 2;
- R.sub.1 is an electron withdrawing substituent inert towards the sulfonium moiety and is stable in the aqueous acid cleaning solutions;
- R.sub.2 is a hydrocarbyl radical of from 1 to about 24 carbon atoms with the provision that R.sub.2 has at least 6 carbon atoms when said sulfonium salt corresponds to I and R.sub.1 is any substituent other than p-nitro;
- R.sub.3 is an alkyl radical of from 1 to 4 carbon atoms, an inertly-substituted alkyl of 2 to 4 carbon atoms, phenyl or inertly-substituted phenyl;
- or R.sub.2 and R.sub.3 are joined to form a 5- or 6-membered heterocyclic ring with the sulfonium atom being the sole hetero atom;
- A.sup..crclbar. is a compatible anion;
- said sulfonium salt being present in an amount at least sufficient to inhibit the acid-induced corrosion of ferrous metals in contact with said solution and ferric ions.
A process of inhibiting the acid-induced and ferric ion-induced corrosion of metal surfaces in contact with an aqueous acid cleaning solution, said process comprising incorporating in said acid solution a sulfonium salt corresponding to the formula ##STR6## wherein n is 1 or 2;
- R.sub.1 is an electron withdrawing substituent inert towards the sulfonium moiety and is stable in the aqueous acid cleaning solutions;
- R.sub.2 is a hydrocarbyl radical of from 1 to about 24 carbon atoms with the provision that R.sub.2 has at least 6 carbon atoms when said sulfonium salt corresponds to I and R.sub.1 is any substituent other than p-nitro;
- R.sub.3 is an alkyl radical of from 1 to 4 carbon atoms, an inertly-substituted alkyl of 2 to 4 carbon atoms, phenyl or inertly-substituted phenyl;
- or R.sub.2 and R.sub.3 are joined to form a 5- or 6-membered heterocyclic ring with the sulfonium atom being the sole hetero atom;
- A.sup..crclbar. is a compatible anion;
- said sulfonium salt being present in an amount at least sufficient to inhibit the acid-induced corrosion of ferrous metals in contact with said solution and ferric ions.
Dependencies are inferred from the claim text.