Composition and method for treating white rust

This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 62/034,960 filed on Aug. 8, 2014.

Galvanized steel has a long history as an effective and economical material of construction for commercial and industrial water systems, including open loop, closed loop, recirculating, and once-through systems, such as cooling towers, chilled water systems, other evaporative cooling systems. Galvanized steel consists of a thin coating of zinc fused to a steel substrate. White rust is a rapid, localized corrosion attack on zinc that usually appears as a voluminous white deposit. This raid corrosion can completely remove zinc in a localized area with the resultant reduction in equipment life.

There are several known compositions for treating white rust, particularly white rust on galvanized steel components in commercial and industrial water systems. For example, U.S. Pat. Nos. 5,407,597 and 6,468,470 disclose compositions comprising organophosphorus compounds (including 2-phosphonobutane-1,2,4-tricarboxylic acid, “PBTC”), an alkali metal salt of molybdenum, titanium, tungsten, or vanadium, and either a carbamate compound or a tannin compound. U.S. Pat. No. 6,183,649 discloses a white-rust treatment composition comprising PBTC, sodium polyacrylate, sodium tolytriazole, an alkali metal molybdate, and an alkali metal bromide for treating circulating water systems. The '649 patent also discloses the addition of a 1.5% aqueous solution of decyl thioethyletheramine (DTEA) at a rate of 25 lb/1,000 gallons of water/week to the circulating water system prior to adding the white rust treatment composition at a rate of 600 ppm per cycle for ten cycles of recirculation after addition of the DTEA.

Another example is found in U.S. Pat. No. 7,851,655, which discloses white rust treatment compositions comprising various amine compounds, such as the reaction products of Jeffamine® (containing oxypropylene) with glycidol(2,3-epoxy-1-propanol). U.S. Pat. No. 8,585,964 discloses a synergistic blend of 0-10% by weight of an amine-based white rust inhibitor (including those disclosed in the '655 patent) and 10-90% by weight of a benzotriazole. The composition of the '964 may also include a fluorescent tracer to track dosage level.

Other methods used in the field include carbonate ion control by bleed-off or acid use. A problem associated with acid use is that manufacturers typically will not warranty systems if acid is used. Additionally, bleed off control results in more water usage.

Another amine-based corrosion and white rust treatment is disclosed in U.S. Pat. No. 2,333,206. The '206 patent is directed to treatment of metal surfaces in atmospheric conditions (rather than surfaces exposed to flowing water contact in an industrial water system) by applying acrylic, aliphatic amines to metal surfaces to provide a spread thickness of 10,000 to 80,000 sq. ft./lb of amines. One of the amines disclosed in the '206 patent is 9,10-octadecenylamine.

According to one preferred embodiment of the invention, an improved white rust inhibitor comprises a mixture of commerically available treatment products. These commercially available products are Cetamine V217 S and Chem-Aqua 31155, which have previously been used to treat industrial and commerical water systems, but not previously used in combination as a treatment for white rust. Cetamine V217 S is a liquid, all-organic product that prevents corrosion through film forming amines and neutralizing amines. The corrosion inhibition of Cetamine V217 S is based on formation of a protective film by adsorption of the filming amine on the surface by its nitrogen atoms. The stabilizing and dispersing effect of Cetamine V217 S prevents the formation of scale by blocking crystal growth. Chem-Aqua 31155 is PBTC/Polymer/TTA blend used as a scale inhibitor in cooling towers.

According to one preferred embodiment, Cetamine V217 S is used in concentrations of around 25-1000 ppm in combination with around 50-150 ppm for Chem-Aqua 31155. More preferably, Cetamine V217 S is used in concentrations of around 200-500 ppm in combination with around 100-150 ppm for Chem-Aqua 31155.

The system of the invention is further described and explained in relation to the following drawings wherein:

FIG. 1 is a photograph of a coupon before treatment and showing no white rust deposits;

FIG. 2A is a photograph of a coupon after two days of treatment with only Chem-Aqua 31155 at 150 ppm;

FIG. 2B is a photograph of the coupon of FIG. 2A after one week of treatment;

FIG. 2C is a photograph of the coupon of FIGS. 2A and 2B after two weeks of treatment;

FIG. 3A is a photograph of a coupon after two days of treatment with Cetamine V217S at 200 ppm and Chem-Aqua 31155 at 150 ppm;

FIG. 3B is a photograph of the coupon of FIG. 3A after one week of treatment;

FIG. 3C is a photograph of the coupon of FIGS. 3A and 3B after two weeks of treatment;

FIG. 4A is a photograph of a coupon after two days of treatment with Cetamine V217S at 300 ppm and Chem-Aqua 31155 at 150 ppm;

FIG. 4B is a photograph of the coupon of FIG. 4A after one week of treatment;

FIG. 4C is a photograph of the coupon of FIGS. 4A and 4B after two weeks of treatment;

FIG. 5A is a photograph of a coupon after two days of treatment with Cetamine V217S at 500 ppm and Chem-Aqua 31155 at 150 ppm;

FIG. 5B is a photograph of the coupon of FIG. 5A after one week of treatment; and

FIG. 5C is a photograph of the coupon of FIGS. 5A and 5B after two weeks of treatment.

Several lab tests were run to test the effectiveness of the Cetamine V217 S and Chem-Aqua 31155 treatment. A Spinner Test Setup consisting of four stainless steel containers with four galvanized coupons installed in each container on holders hanging from a rotating shaft. The shaft rotates at 147 rot/min, which rotates the coupons around the steel container to simulate the flow of water over a galvanized component in a flowing water system, such as a cooling tower. The simulated flow rate was around 3-5 ft/s depending on coupon's distance from the center of the rotating shaft. Several tests were run using differing water conditions and differing treatment levels, as described below, but each test was conducted for around 48 hours and with a water temperature of around 120 F and water aeration of around 5 standard cubic feet per hour.

The tests were run using two different water chemistries: low LSI (Langelier Saturation Index, the higher the LSI the more potential for white rust formation) corrosive water and water with hardness, having the properties listed below in Table 1. A first test was run using only Chem-Aqua 31155 added to the containers of water at 150 ppm, and second-fourth tests were run with Chem-Aqua 31155 at 150 ppm and the white rust inhibitor Cetamine V217 S was added at various levels (200 ppm, 300 ppm, and 500 ppm, respectively) based on manufacturer recommendations. Prior to adding the galvanized coupons to the containers with water, the coupons cleaned with a supersaturated ammonium acetate solution, followed by water and IPA (isopropyl alcohol) rinse. Coupon weight was recorded before use and after the cleaning and MPY (mils per year) corrosion rates were determined.

FIG. 1 shows a coupon before any treatment—ACT Hot Dip Galvanized G70 (length=4″, width=1″, thickness=0.03″). FIG. 2A shows a coupon after two days of treatment with only Chem-Aqua 31155 at 150 ppm in a hard water container. FIGS. 2B and 2C show the same coupon after 1 week and 2 weeks of treatment, respectively, with only Chem-Aqua 31155 in a hard water container. White rust is visually manifested as white, fluffy sometimes “waxy” deposits on wetted galvanized steel. As can bee seen, the formation of white rust is visible after 2 days of treatment with CHem-Aqua 31155 at 150 ppm ( FIG. 2A ) and is extensive by 1 week ( FIG. 2B ). By the end of two weeks, the coupon is almost entirely covered with white rust as shown in FIG. 2C .

FIGS. 3A-3C show coupons after two days, 1 week, and 2 weeks, respectively, of treatment with Chem-Aqua 31155 at 150 ppm and Cetamine V217S at 200 ppm in a hard water container. Although there was some white rust formation after 2 days, the amount of white rust was less than on the coupon treated with only Chem-Aqua 31155 ( FIG. 2A ). The difference in white rust formation comparing the Chem-Aqua 31155 only treatment ( FIG. 2B ) to the combination of Cetamine V217 S and Chem-Aqua 31155 ( FIG. 3B ) after 1 week of treatment was even greater.

FIGS. 4A-4C similarly show coupons after two days, 1 week, and 2 weeks, respectively, of treatment with Chem-Aqua 31155 at 150 ppm and Cetamine V217S at 300 ppm in a hard water container. Again, although there was some white rust formation after 2 days, the amount of white rust was less than on the coupon treated with only Chem-Aqua 31155. At this treatment concentration level, the amount of white rust formation at two weeks is only slightly greater than at 1 week and the two-week level is far less than either the two-week level when Cetamine V217 S is used at a concentration of 200 ppm with Chem-Aqua 31155 at 150 ppm or when Chem-Aqua 31155 is used alone.

FIGS. 5A-5C similarly show coupons after two days, 1 week, and 2 weeks, respectively, of treatment with Chem-Aqua 31155 at 150 ppm and Cetamine V217S at 500 ppm in a hard water container. As can be seen, the results in preventing white rust formation are even better at these concentrations.

These lab studies demonstrate that the combination of Cetamine V217 S and Chem-Aqua 31155 is effective at protecting galvanized metal from white rust deposition. As shown in the Figures, after two days of treatment with Cetamine V217 S/Chem-Aqua 31155, the coupons have far less white rust on their surface relative to the ones treated with only Chem-Aqua 31155. After a week of treatment, coupons treated with only Chem-Aqua 31155 are almost totally covered with typical white rust corrosion product, while the coupons treated with Cetamine V217 S and Chem-Aqua 31155 have very little white rust corrosion product and show a significant amount of original, undamaged metal surface. Cetamine V217 S at various levels (200, 300, 500 ppm) proved to be very effective at preventing white rust corrosion even after two weeks. Higher levels of Cetamine V217 S, up around 1000 ppm, are even more effective.

Chem-Aqua 31155, commerically available from Chem-Aqua, Inc., is a PTSA traced PBTC/PolymerITTA blend that is currently used for calcium carbonate scale control under high stress conditions and has a pH of 12.1. MSDS information for Chem-Aqua 31155 lists its ingredients as indicated in Tale 2 below.

Cetamine V217 S is commerically available from BK Giulini (BK Water Solutions) Germany and distributed by ICL Water Solutions. MSDS information for Cetamine V217 S indicates that it is a liquid, water soluble, all organic corrosion inhibitor for steam boilers with a pH or 1% solution of 10.0 have the primary ingredients listed in Table 3 below:

Oleylamine has the molecular formula C18H35NH2 and is also known as (Z)-Octa-9-decenylamine (CAS number 112-90-3) and is similar in structure to a fatty oleic acid. The structure of oleylamine is shown below:

In one preferred embodiment of the invention, an improved white rust inhibitor comprises a mixture of a first composition (or component) and a second composition (or component). The first composition preferably comprises around 2.5-10% 2-diethylaminoethanol (DEAE), around 2.5-5% cyclohexylamine at 2.5-5%, 0-2.5% oleylamine ((Z)-octadec-9-enylamine). The second composition preferably comprises 40-60% DI water, 2-10% K-7028 (sodium polyacrylate), 10-20% NaOH 50% pt. 1, 5-15% NaTT 50% (sodium tolytriazole), 1-5% Belclene 200 (polymaleic acid sodium salt), 5-15% PBTC 50% (2-phosphonobutane-1,2,4 tricarboxylic acid, sodium salt), and 0.5-1.5% NaOH 50% pt. 2. Optionally, the second composition may comprise around 0.5-1.5% Spectra Trace SH-L or another flourescent tracer. Preferably, the white rust inhibitor comprises between 25-1000 ppm of the first composition and between 50-150 ppm of the second composition. Most preferably, the white rust inhibitor comprises between 200-500 ppm of the first composition and between 100-150 ppm of the second composition.

In another preferred embodiment, an improved white rust inhibitor comprises a combination of commerically available products: Cetamine V217 S and Chem-Aqua 31155. Preferably, the white rust inhibitor comprises between 25-1000 ppm of Cetamine V217 S and between 50-150 ppm of Chem-Aqua 31155. Most preferably, the white rust inhibitor comprises between 200-500 ppm of Cetamine V217 S and between 100-150 ppm of Chem-Aqua 31155.

Water systems are treated by adding the composition according to the invention to achieve concentrations of treatment composition according to the above amounts. Periodic re-treatment may be needed to maintain concentration levels within the preferred treatment ranges. Those of ordinary skill in the art will understand that the other suitable or equivalent chemical compounds may be substituted for any of the above ingredients within the scope of this invention.