Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids

Definitions

• This invention relates to corrosion control in steam condensate systems and other aqueous systems in which the mineral content is relatively low.
• this invention relates to the use of methoxypropylamine in combination with hydrazine to control corrosion in stream condensate systems or in other low solids aqueous systems.
• a greater corroding influence than the mere dissolving tendency of iron is the existence of a heterogeneous surface in commercial iron and steel due to the presence of surface imperfections which tend to form couples with the adjacent base metal. Electrons are released from the anodes of these couples to the hydrogen ions at the adjacent cathodic surface, thus increasing the corroding area and accelerating the rate of corrosion.
• the first product of corrosion may be converted to ferric oxide, which is only loosely adherent and aggravates corrosion by blocking off areas to oxygen access. These areas become anodic and iron oxide couples are set up. The iron under the oxide deposit then dissolves, and pitting develops. Carbon dioxide attack results in thinning or grooving of the metal.
• filming amines will give condensate corrosion protection against both oxygen and carbon dioxide.
• many industrial systems cannot tolerate filming amines and must use neutralizing amines.
• Neutralizing amines such as cyclohexylamine and morpholine have been used but they have several disadvantages.
• cyclohexylamine has a high distribution ratio and accordingly, substantial cyclohexylamine escapes the system through the deaerator vent.
• Morpholine has a low basicity value which means that more morpholine is required to attain high pH's in the condensate system and it also has a very low distribution ratio which means that substantial amounts are lost via blowdown.
• the neutralising amine of this invention overcomes the above-mentioned disadvantages of cyclohexylamine and morpholine.
• Methoxypropylamine has a very desirable distribution ratio and a fairly high basicity value.
• Methoxypropylamine may be used alone or in combination with an oxygen corrosion inhibitor such as hydrazine. In use, concentrations of 0.1 to 1000 mg/I, and preferably 1 to 100 mg/I, should be maintained in the steam condensate system. When used in combination with hydrazine or another oxygen corrosion inhibitor, the composition should contain on an active basis from about 1 % to about 99% methoxypropylamine and from about 0.1% to about 50%, preferably about 1 % to about 15%, of the oxygen corrosion inhibitor.
• the compositions of this invention may be fed to the steam condensate system being treated by conventional liquid feeding means or may be fed to the boiler feedwater or directly to the steam supply lines.
• Distribution ratios of a number of neutralizing amines were calculated by preparing solutions of each amine having a concentration of 100 mg/I and adding 500 ml of this solution to a brine pot which is slowly and uniformly heated so that 100 ml of distillate is produced every 40 minutes. Additional solution is manually introduced to the brine pot every 5 to 10 minutes to maintain the brine pot solution at the 500 ml mark. Each 100 ml aliquot of distillate is collected and pH determined until constant pH is attained for three successive aliquots. This is taken to represent the establishment of equilibrium conditions. At equilibrium, the brine and the final 100 mls are analyzed by gas chromatography to determine the amount of amine in each and the Distribution Ratio (D.R.) calculated by the following formula:
• K b the basicity value or measure of the amine's ability to react with carbon dioxide is calculated in accordance with the formula: wherein [BH + ], [OH - ] and [B°] are defined as:
• the hydrolytic-thermal stability of various neutralizing amines is measured by a test in which the neutralizing amine at a concentration of 1000 mg/I is autoclaved for 24 hours at 41 bar (600 psi) at 254°C (489°F) and the final concentration of ammonia measured. The results of this test are set forth in Table II.
• a condensate test system is used to evaluate neutralizing amines.
• This system comprises a boiler capable of producing 45 kilograms/hour of a steam at pressure of 13,7 bar (200 psi), pumps and metering devices to control the composition of the make-up water to the boiler, and cooling coils with temperature control means to condense the steam.
• the condensate is recirculated through a test loop where metal coupons and corrosometer probes evaluate the corrosion rate.
• the test water is distilled water containing ⁇ 1 mg/l S0 4 , ⁇ 1 mg/I CI, ⁇ 1 mg/l Si0 2 and 10 mg/I CO 2 . Table III sets forth the results of corrosion tests in this system.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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Publications (2)

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• 1978
  • 1978-10-31 CA CA315,596A patent/CA1105695A/en not_active Expired
  • 1978-12-04 EP EP78400209A patent/EP0002634B1/en not_active Expired
  • 1978-12-04 DE DE7878400209T patent/DE2860673D1/de not_active Expired
  • 1978-12-05 AU AU42203/78A patent/AU521299B2/en not_active Expired
  • 1978-12-11 DK DK556378A patent/DK152766C/da not_active IP Right Cessation
  • 1978-12-11 IE IE2443/78A patent/IE47613B1/en not_active IP Right Cessation
  • 1978-12-12 JP JP15277978A patent/JPS5492535A/ja active Granted
  • 1978-12-12 IT IT52260/78A patent/IT1107785B/it active

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