DE60312202T2 - METHOD OF INHIBITING THE INTERKRISTALLINE CORROSION OF METAL SURFACES - Google Patents

Abstract

The present invention is directed toward the use of a reaction product of an alkynediol and a polyalkylene polyamine to inhibit intergranular corrosion of metal surfaces in industrial processing systems caused by spray water mist or condensation.

Description

AREA OF INVENTION

The The present invention is directed to the use of the reaction product of alkynediols and polyalkylenepolyamine compounds to intergranular corrosion of metal surfaces to inhibit in industrial water and process systems whose surfaces in contact with splashing water or condensation.

BACKGROUND THE INVENTION

The Microstructure of metals and alloys is made up of grains, separated by grain boundaries. Intergranular corrosion can be localized as Attack along the grain boundaries or directly adjacent to grain boundaries To be defined. Such excretion can be zones of reduced Corrosion resistance in create the immediate neighborhood.

One example for Intergranular corrosion is the sensitization of stainless steels or Weld decay. Chromium rich grain boundary precipitations lead to a local depletion from Cr near this Precipitates, making these areas prone to corrosive attack.

exfoliation corrosion is a special form of intergranular corrosion. Peeling off or Delamination presents itself as a loss of metal in layers which seems to follow grain boundaries along the surface. The peel in the rollers occurs e.g. in non-humid structures of the lower Segments on where direct splash contact does not occur. Of the Steel is one hot, exposed to moist environment, in which the surfaces only by spray water mist or condensation moistened. The corrosion progresses quickly along the steel surfaces resulting in loss of structural integrity of the secondary support structure results.

Of the Mechanism for exfoliation corrosion is linked to the presence of chlorides in the spray. If used in the spray water system, the fog (steam) travels through the steam chamber and focuses on steel surfaces. The Heat and Moisture evaporates the water from the steel surface, which leaves a concentrated chloride ion behind. This process is going on continue, with more and more chloride ions being concentrated until to the point of flaking off occurs.

sample analysis indicates that the corrosion mechanism occurs as follows: the chloride ion, that on the metal surface is deposited through the brittle layer of corrosion product / deposit, which is generated. Under the deposit, a transition iron chloride salt is generated. The salt is hygroscopic (moisture absorbing) and is subject to Hydrolysis, which produces acidic chloride conditions. additional Iron oxide corrosion products are left behind when the acidic Corrosion front penetrates deeper into the metal surface.

in the In view of what has been said, the industry is looking for techniques and inhibitors to exfoliate corrosion, which is present in industrial processing systems.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The The present invention is directed to methods of inhibition intergranular corrosion of metal surfaces in industrial processing systems, e.g. Steam and cooling water systems, their surfaces In contact with splashing or condensation, which are the addition a sufficient corrosion inhibiting amount of the reaction product from an alkynediol and a polyalkylenepolyamine to the spray exhibit.

The Conditions under which the reaction product is formed are in U.S. Patent No. 3,211,667, the contents of which are hereby incorporated by reference becomes.

The Alkynediols and alkenediols which are taught to be effective are in the production of the reaction product, are those that four to twelve Contain carbon atoms. Preferably, the alkynediols contain four carbon atoms. An exemplary alkynediol is butynediol.

The polyalkylenepolyamine compounds taught to be effective in the preparation of the reaction product are those containing two to ten amine groups, and preferably three to three seven amine groups. These amine groups may be substituted or unsubstituted and are each separated by an alkylene group having from one to six carbon atoms, with two to four preferred. Exemplary polyamines include ethylenediamine, diethylenetriamine, pentaethylenehexamine, pentapropylenehexamine, triheptylenediamine, and the like.

The weight ratio the reactant is such that complete reaction between the respective ingredients, with weight ratios from amine to diol from 4: 1 to 1: 1, with 3: 1 being preferred. A ionizable compound of copper, e.g. Copper acetate, is used in this reaction in catalytic amounts.

The Reaction product of the present invention may be added to the spray water be added in an amount sufficient to corrosion the metal surfaces to inhibit. The reaction product can via a supply line in a Amount in the range of 0.5 parts to about 500 parts per million parts Water present in the supply line may be added. Preferably, about 1 to 100 parts per million parts of water added, with about 5 to 10 parts per million parts of water especially are preferred.

The Reaction product of the present invention is introduced into the feed line either in a solvent or added in pure form. Preferably, the reaction product becomes in an aqueous solvent added, of which water is an example. The reaction product can add to the spray water along with other suitable ingredients, such as. Antifoams, corrosion inhibitors and the like, be added. The splash water in the systems to be treated typically has a temperature of about 43.3-82.2 ° C (110-180 ° F).

The Data listed below are, show the unexpected results by using this Be caused invention. The following examples are called Illustrative of the invention included and not intended intended to limit their scope.

Examples

• (*) 1 mpy (Milliinch pro Jahr) entspricht 25,4 Mikrometern pro Jahr

In order to prevent the corrosion mechanism from occurring on metal surfaces, the addition of a film-forming material is suggested to isolate the surfaces of water and chlorides. The addition of 2-butyne-1,4-diol-polyethylenepolyamine (product A) significantly reduces corrosion rates of steel (as shown in Tables 1 and 2). In all tests, coupon trees are created to place a variety of corrosion sections within a spray chamber. The solution is injected into the supply line to the caster sprays. This distributes the material in the injection chamber: Table 1 (Sections, submitted for SEM)

• (*) 1 mpy (milli per year) equals 25.4 microns per year

The Iron amount is greatly reduced in the deposit.

Table 2 (Sections, submitted for SEM)

The Results show that during the chloride concentration for both the untreated (5%) and treated page (6%) similar was, the other components are dramatically different. Of the Iron content of the untreated side is 88%, the content of exfoliation is also significant. On the treated side is the iron content only 23% and exfoliation is none available. The treated side has 52% calcium what the Indicating the presence of corrosion inhibition.

In additional Tests a corrosion section is immersed in product A and next to an untreated section in both the treated as also untreated strands placed. The untreated strand shows the immersed section very little corrosion while the untreated section peels off. There was a significant improvement in the treated strand in the corrosion control opposite the non-immersed section.

at Other studies of the present invention have been made alternative section trees constructed. Section tests include: mild steel, stainless steel, Copper and coated structural steel.

One a single set of structural steel sections will become a first after eight days Examination removed. Section results are shown in Table 3 below shown. Sections of Strand # 2 show signs of flaking, while sections of strand # 1 merely show general corrosion mechanism.

Table 3 - Section Results after eight days (mpy)

As Still shown in Table 4 below, there is a significant reduction in the speed of corrosion in the corrosion section tree in strand # 1, where product A is injected. Product A is with 15 ppm fed into the system.

Mild steel corrosion rates are reduced in most places by about 50 to 80%. As Above, sections of Strand # 2 show signs of flaking, while sections of strand # 1 merely show general corrosion mechanism (flaking is not present).

Table 4 - Section Corrosion Results (mpy)

you Note that all remaining sections are either more stainless Steel or coated sections were. No significant corrosion was visible on any of these sections. In addition, the affected Treatment according to the invention not detrimental to the nozzle performance in the spray water system.

While the Invention has been described with reference to its particular embodiments, It is obvious that a variety of other forms and Modifications of this invention will be apparent to those skilled in the art are. The attached claims and this invention in general should be construed as all such obvious forms and modifications that are within the true spirit and scope of the present invention, are covered.

Claims (13)

Method for inhibiting intergranular corrosion of metal surfaces in industrial processing systems, with the surfaces in Contact with splashing water is what procedure involves that one the spray water sufficient to inhibit corrosion Amount of the reaction product of an alkynediol and a polyalkylenepolyamine adds. The method of claim 1, wherein the intergranular corrosion layered Corrosion is. The method of claim 1, wherein the metal surfaces are continuous Include casting surfaces. The method of claim 2, wherein the layered corrosion on metal surfaces happens, which is wetted by spray mist or condensation are. The method of claim 1, wherein the alkynediol is a Alking group contains, which has 4 to 12 carbon atoms. The process of claim 1 wherein the alkynediol is butynediol is. The method of claim 1, wherein the polyalkylenepolyamine Contains 2 to 10 amine groups, each separated by an alkylene group from each other, the 1-6 Has carbon atoms. The method of claim 1, wherein the polyalkylenepolyamine Pentaethylenehexamine is. The method of claim 1, wherein the reaction product the spray water in an amount ranging from 0.5 parts to about 500 parts per million of water is added. The method of claim 1, wherein the spray water a temperature of about 43.3 ° C (110 ° F) up to about 82.2 ° C (180 ° F) Has. The method of claim 1, wherein the reaction product the splash in an aqueous solvent added becomes. The method of claim 1, wherein the metal surfaces are iron containing metal surfaces are. The method of claim 1, wherein the industrial processing methods are steam and cooling water include systems.