corrosion of copper and copper alloys in potable water systems

Corrosion of Copper Alloys in Potable Water Systems

NACE Central Area Conference October 1-4, 2006

By:

David E. Hendrix, P.E. The Hendrix Group Inc.

Houston, TX.

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• Who has copper plumbing in their home?

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• What we will learn: – Short history of copper use and production – A Little about copper and copper alloy systems – Why coppers for potable water/plumbing systems – Pitting corrosion of coppers in potable waters – SCC of coppers in potable waters – Dezincification of coppers in potable waters – Case histories illustrating failures of coppers in potable waters

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• Copper probably first came into use as the earliest non-precious metal employed by the Sumerians and Chaldeans of Mesopotamia, after they had established their thriving cities of Sumer and Accad, Ur, al'Ubaid and others, somewhere between 5,000 and 6,000 years ago.

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• Homer, following the Greek practice of around 1000 B.C., called the metal Chalkos; hence the Copper Age is also known as the Chalcolithic. Finally, after another thousand years had elapsed, the words "aes Cyprium" appear in Roman writings of the Early Christian Era because so much of the metal came from Cyprus. 'Copper' is the anglicized version of this Latin phrase.

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• The earliest definite date usually assigned to true bronze casting is about 2500 B.C., i.e. 700 years or more after copper is known to have been in use.

• The early coppersmiths learned that when hammered,

copper hardened and, conversely, by heating it softened again.

• When some unknown inventor conceived the idea of deliberately adding fixed proportions of tin ore to the melt, he produced true bronze and thereby started the Bronze Age.

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• The Romans were the first to use brass on any significant scale, although the Greeks were well acquainted with it in Aristotle's time (c. 330 B.C.). They knew it as 'oreichalcos', a brilliant-and-white copper, which was made by mixing tin and copper with a special earth called 'calmia' that came originally from the shores of the Black Sea.

• Pure zinc was not known until quite modern times, the ore employed being calamine which is an impure zinc carbonate rich in silica.

• The earliest brass was made by mixing ground calamine ore with copper and heating the mixture in a crucible. The heat applied was sufficient to reduce the zinc to the metallic state but not to melt the copper. The vapor from the zinc, however, permeated the copper and formed brass which was then melted.

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• Until recently copper ore had to be hand-picked if the extraction of the metal was to be economical.

• Today the great majority of mines contain the metal in finely disseminated particles which aggregate anything from 2 % to 1% of copper.

• To obtain metallic copper, up to 99 percent of the material mined must be removed as waste.

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• Only the flotation process can make this practicable; and even so, it requires large companies with huge plants, continuous working and immense capital. In order to smelt 4 million tons of new copper in 1963, nearly 400 million tons of ore have to be handled and treated in various ways.

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• The product of flotation is called 'concentrate'. It is passed on to the smelter and, after further processing, refining is done in great batteries of electrolytic tanks.

• The final products of smelting and electrolytic refining are cathodes, cast often in the form of copper wirebars and cakes.* The casting are subsequently worked in various ways into wrought forms. Re-melted cathodes may also be cast into ingot bars suitable for the preparation of alloys.

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• The industrial importance of copper in the 20th Century has been extended by the ease with which it combines with other metals. Tin and zinc are and always have been the principal alloying elements, but there are now many others - aluminum, beryllium, chromium, manganese, etc. - which form alloys with special mechanical and physical properties.

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• Copper was first used by man over 10,000 years ago. • For nearly five millennia copper was the only metal known

to man, and thus had all the metal applications. • Early copper artifacts were hammered out from pure copper

found in conjunction with copper-bearing ores in a few places around the world.

• By 5000 BC, the dawn of metallurgy had arrived, as evidence exists of the smelting of simple copper oxide ores such as malachite and azurite.

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• By 3000 B.C., silver and lead were being used and the alloying of copper had begun, first with arsenic and then with tin.

• Copper came from the island of Cyprus-from whence its name.

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• The Bronze Age suddenly ended at about 1200 BC, with the general collapse of the ancient world and the interruption of international trade routes. The supply of tin dried up and the Iron Age was ushered in, not because iron was a superior material, but because it was widely available.

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• Due to its high strength, durability and superior heat-transfer capabilities, copper has long been the material of choice for both residential and commercial plumbing and heating systems.

• 80% of homes in the United States use copper pipe and fittings.

• More than 9 out of 10 plumbers (94%) use copper tube in their own homes.

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• "Homeowners typically do not worry about their plumbing, but maybe they should," says CDA president Andrew G. Kireta, Sr. "It's basically an 'out-of-sight, out-of-mind' issue.

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• Why is copper popular for plumbing applications? – Malleable – Easily joined (soldering) – Impermeable – Won’t burn or melt in a fire (residential fires) – Biostatic – Inhibits growth of harmful bacteria

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• Lead has traditionally been used in cast brass plumbing fixtures to improve machineability and to ensure pressure tightness.

• Pressure tightness is achieved because lead fills intradendritic voids in castings.

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• Cast red and yellow brasses contain a fine dispersion of lead particles.

• This dispersed lead improves machineability of brass castings by acting as a cutting tool lubricant. – Lead provides weak points or notches in otherwise continuous

chips, which facilitate their breakages into smaller segments. This allows machines to run at high speeds and keeps machining costs low.

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• The most common plumbing brass, UNS Alloy C84400, a semi-red brass where 3, 7 and 9 represent the nominal amounts of tin, lead and zinc in the alloy.

• The most popular red brass, UNS Alloy C83600 is known as

85 metal or 85-5-5-5. In this alloy, the tin, lead and zinc contents are equal and are 5% each.

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• Copper plumbing tube has been the industry standard in the U.S. for the last half century.

• By any measure, copper has been very successful as a plumbing tube material. However, failures do occur, but they are few and infrequent.

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Copper and Copper Alloy Systems

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Wrought Alloys:

Coppers(C10100 - C15999) ***

High Copper Alloys(C16000 - C19999)

Brasses(C21000 - C49999) ***

Bronzes(C50000 - C69999)

Copper Nickels(C70000 - C73499)

Nickel Silvers(C73500 - C79999)

Cast Alloys:

Coppers(C80000 - C81399)

High Copper Alloys(C81400 - C83299)

Brasses(C83300 - C89999)

Bronzes(C90000 - C95999)

Copper Nickels(C96000 - C96999)

Nickel Silvers(C97000 - C97999)

Leaded Coppers(C98000 - C98999)

Special Alloys(C99000 - C99999)


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Coppers(C10100 - C15999)

C21000-C28999 Copper-Zinc Alloys(Yellow Brasses)

C30000-C39999 Copper-Zinc-Lead Alloys(Leaded Brasses)

C40000-C49999 Copper-Zinc-Tin Alloys(Tin Brasses)

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Corrosion of Coppers in Potable Waters

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• “A great deal, but not everything, is known about corrosion of copper, but theories that have little scientific basis are constantly surfacing.”

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Copper corrosion failures by category.

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• Results of a Copper Development Association (CDA) symposium on copper plumbing tube pitting. – Aluminum coagulant water treatments increases general

corrosion but not pitting. – Aluminum and chlorine can act synergistically in regard to

corrosion (a source of aluminum includes Portland cement lined pipe, which contains 5% aluminum).

– Pitting has not been reproduced in the laboratory. Water, which has caused pitting in the actual installations, has been taken back to the laboratory and used in testing, but pitting has not been observed. This implies that copper pitting in potable water is not a completely understood phenomenon.

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• Microbial induced corrosion (MIC) does occur in copper even though copper is macro-fouling resistant and has well documented biostatic/biocidal properties.

• When copper fails, it is usually a result of factors outside the designer's knowledge and control.

• Corrosion on the internal surfaces of tubes is typically associated with contaminants such as excessive flux from soldering. Also, improper chlorination may cause pitting, and chlorination, in combination with residual flux, can result in rapid perforation, sometimes in a matter of days.

• Other factors, such as high operating velocities, and burrs or lips remaining on unreamed cut ends of soldered tubes can lead to erosion failures.

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• Aggressive "pitting waters" are characterized as having a pH range of 7.2 to 7.8, high content of CO2, (over 10 ppm), high total dissolved solids including sulfates and chlorides, and the presence of dissolved oxygen gas.

• A coherent theory, that allows prediction or prevention of copper pitting, is currently lacking".

• Flux plays a large role in pitting perforations. • A variety of human causes are responsible They include

failures related to flux, erosion downstream of burrs, incomplete soldering leading to crevices, microbiological action and debris leading to underdeposit corrosion.

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• One presenter reported on the cause of extensive pitting observed in a new hotel in the Middle East after only one year.It was determined that water quality was a major factor in the observed failures.

• It was known that a reverse osmosis plant supplied the water, which was heated and recirculated in a closed loop.

• The ID surface was covered with a light green scale with scattered islands of heavy blue-green deposits (chlorine, sulfur and to a lesser extent, silicon.)

• It was concluded that the water quality was less than ideal and the high concentrations of contaminants, which can be aggressive to copper were present.

• So What!

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• Conclusions from the Symposium on Pitting of Copper Plumbing Tube

– by any measure, copper is a very successful plumbing tube

material. – failures do occur, but they are few and infrequent. – pitting has not been reproduced under controlled laboratory

conditions. – a coherent theory that allows prediction or prevention of pitting

is currently lacking. – flux induced attack is a major cause of pitting. – pitting can occur under deposits, and crevice attack can be

observed in incompletely filled joints.

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– erosion failures are a result of poor design and installation, as well as operating at excessive velocities.

– MIC is increasing because of increasing recognition as a distinct form

of corrosion, decreasing residual chlorine levels, extended lay-up times during hydrostatic testing, and higher levels of suspended solids related to phosphate scale-control programs.

– MIC can be mitigated by cleaning to remove organic deposits, use of

biocides-after cleaning if possible, avoiding stagnant conditions, using thermal shock, eliminating nutrient sources, and increasing pH.

– corrosion can be mitigated if:

• systems are designed so that velocities do not exceed 4 to 5 fps ( 1.2 to 1.5 mps ) in circulating systems.

• copper tubing systems are properly installed, without he use of excessive or unusually aggressive fluxes.

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• hot water heater/storage tank corrosion is prevented. • the water purveyor distribute quality product which does not

contain unacceptable amounts of suspended solids, dissolved carbon dioxide, microorganisms, aluminum, dissolved hydrogen sulfide and / or iron.

• systems are operated within design parameters including

safe and energy-efficient hot water temperatures between 120F and 130F (49C and 54C).

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• Types of Copper Corrosion

– Type I – (Cold water pitting)* – Type II – (Hot water pitting* – Rosette corrosion – MIC – Erosion-Corrosion* – Flux-induced corrosion – Stress corrosion cracking* – Dezincification*

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Erosion-Corrosion

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• Erosion-Corrosion – Typically occurs in recirculating systems. – A typical hot water recirculating system consists of a piping

loop in which hot water, from hot water tanks or boilers, is kept circulating by one or more pumps. This permits hot water to reach most points in the building within relatively short periods of demand time.

– Several factors contribute to the corrosion:

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• Several factors contribute to the corrosion: – Water velocities exceeding 5-feet per second. – Undersized distribution lines, creating high velocities. – Oversized circulating pumps with no bypass. – Multiple and/or abrupt changes in direction – Failure to remove the burr on the inside of the tube after cutting. – Improper solder or brazed joints. – Improper use of throttling valves for system balancing.

• Excessive velocity in a hot water recirculating system is typically

the result of using an oversized pump, or undersized distribution lines.

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Copper Corrosion vs. Velocity

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• Recommendations to eliminate erosion-corrosion – Design all hot water recirculating systems to keep velocities

below 5 feet per second for temperatures up to 60oC – Flow maximums should not exceed 3 to 4 feet per second for

water >60C. – Make all solder joints according to ASTM B828, "Making

Capillary Joints by Soldering of Copper and Copper Alloy Tube and Fittings.”

– Reduce dissolved gasses. – Eliminate burrs.

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Pitting Corrosion of Copper

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• Classification of Pitting Corrosion – Type I (Cold water pitting) – Type II (Hot water pitting) – Type III (Soft water pitting)

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• Type I Pitting – Pits deep and narrow – Results in perforation failure – Pits contain Cu2O with over layer of malachite, calcite or

other copper salts (chlorides) – Occurs in hard, cold well waters between pH 7-7.8 – Waters high in sulfates relative to chlorides and

bicarbonates – Stagnation early in life, deposits, high chlorine residuals,

or carbon films

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Type I (Cold water) Pitting

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• Type II Pitting (hot water) – Pits narrower than in Type I pitting – Results in pipe failure – Cu2O in pits with overlayer of bronchantite and malachite – Occurs in hot waters with pH< 7.2 – High sulfates relative to bicarbonates – High temperatures, high chlorine residuals, alum

coagulation.

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Type II (Hot water) Pitting

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• Type III (soft water) pitting – Pits wide and shallow – Blue water, by-products block passages – Cu2O in pits with overlayer of bronchantite and

malachite – Occurs in soft water with pH>8 – Stagnation in early life

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• “In contact with oxygenated drinking waters copper develops a semi-protective corrosion product layer. This usually ensures an economic life and limits the concentration of copper in the water to values well below 2 (mg/l).

• In such waters copper pipe is normally resistant to corrosion.

However, problems can occur if a non-protective layer is formed through prolonged stagnation during a system’s early life and in the presence of certain water characteristics.

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• In water with low oxygen (DO) content (less than 2 mg/l) copper is stable and it will not corrode readily.

• In acidic water (<pH = 6) with high DO (> 2 mg/l), the metal may dissolve to form the copper ion Cu2+ (also called cupric ion), which is the most stable form in these conditions. Such waters are cuprosolvent.

• In neutral to slightly alkaline water (pH 6 - 8) with high DO, the metal may initially produce insoluble cuprous oxide (Cu2O). This magenta, red-to-brown corrosion product is the most stable species in these conditions and will form a semi-protective scale against further corrosion.

• In water with high DO and strongly alkaline (pH > 8), the copper may form cupric oxide (CuO). This jet-black to brown corrosion product is the most stable species in these conditions and will form a semi-protective scale against further corrosion.

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• Where the initial semi-protective scales form, corrosion continues, but at a much-reduced rate.

• A deposit can form on top of the oxide layer which typically consists of basic copper carbonate or malachite (Cu2(OH)2CO3). This deposit has a characteristic turquoise-green color.

• For malachite to be produced, the water needs to contain carbonate combined with high pH.

• The composite deposits are beneficial but can experience localized breakdown leading to different types of pitting corrosion.

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• For the layers to be protective, periods of prolonged static water conditions have to be avoided.

• Systems that have been initially filled but then left standing full of water until the building becomes occupied often give unsatisfactory long-term performance.

• It is recommended that newly completed copper pipework be drained after testing if it is not to be used within a few days.

• If this is not feasible, flushing is recommended at least weekly to avoid loss of the protective layer.

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• Type I Corrosion – Type I pitting (or cold water pitting) is confined to those parts of the

plumbing system < 40°C. – Corrosion deposits are deep green, semi-isolated mounds above

pits or pinholes in the pipe wall. Typically the pipe or cylinder fails in a short period of time, (3-4 years) but sometimes within a few months. Two or more factors need to be present for Type I pitting damage to occur.

– Initiation of pitting is generally related to the condition of the metal before it is exposed to water. Initiation usually occurs due to the presence of a carbon film produced in manufacture.

– The presence of a continuous carbon film, rather than the quantity of carbon present, seems to be the key factor in creating this condition.

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• The propagation of the pit is normally a function of water quality. The water has to have a critical composition that is determined by a combination of six inorganic parameters (DO, sulfate, chloride, nitrate, sodium and pH).

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• Type I pitting does not normally occur under the following conditions: – Water pH less than 7 where more rapid, generalized corrosion

will occur; – In surface-derived supplies which normally contain a natural

organic material that inhibits corrosion – Water with high chloride content (i.e. greater than 60 mg/l)

where more rapid, generalized corrosion will occur – Typical Type I pitting waters are borehole supplies, which are

largely free of organic matter and have pH values in the range 7 to 8.2.

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• Type II Pitting – The potential for Type II pitting occurs in hot water systems

only (i.e. greater than 60° C) and is associated with very soft waters that often contain manganese.

– Type II pitting is much slower than Type I, rarely producing a perforation in less than eight years.

– Characteristic features include deep pits of small cross-section containing very hard crystalline cuprous oxide (Cu2O) capped by small black, or greenish-black mounds of cuprous oxide and basic copper sulfate.

– The occurrence of Type II pitting appears to be primarily related to water quality, but the mechanism is still in question.

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• What to do about Type II Pitting – Not running the system at temperatures above 60° C. – Avoiding oxidizing conditions such as over chlorination or

entrainment of air in the system. – Keeping the pH below 7.5.

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Duplex Film Model of Copper Corrosion

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Model of Copper Pit Morphology

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Copper Corrosion vs. pH

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Dezincification of Copper Alloys

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• Dezincification, was first recognized in the late 1950s. • In its simplest form, dezincification was evident with brass

nuts on tap washers. While in service, the affected nuts turned pink and disintegrated when the washer was being changed.

• More serious was the corrosion of fittings and valves, which exhibited a build up of visible white or blue/green deposits before they leaked.

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• It was discovered that the corrosion occurred due to the composition of some waters reacting with particular brass alloys (copper and zinc).

• Brasses with high zinc content were the ones that suffered

dezincification when exposed to aggressive water.

• Brasses with >15% zinc the most susceptible to dezincification.

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• The affected metals consisted of two phases and it was the zinc rich phase that was attacked, with zinc being leached from the metal and the copper being re-deposited in a pink, spongy, brittle form.

• Whitish deposits, attached to failed valves, consisted of

zinc-rich products.

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Waters Causing Dezincification

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• Dezincification resistant brasses – First generation brasses inhibited with Antimony or Arsenic

• C44300, C44400, C46500

– The above not immune to dezincification!

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• As a result of comprehensive research, laboratory tests and field trials, dezincification resistant (DR) brass was developed.

• Inhibition to dezincification was achieved, without affecting the intrinsic properties of brass, by adding small amounts of certain elements to the alloys.

• The metals were also processed in such a way as to reduce the size of the boundaries of the susceptible zinc-rich phase to minimize the potential for attack.

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Dezincification resistant brass • Brass contains a mixture of alpha and beta phases, and a

fine distribution of lead particles, which impart excellent machineability.

• In binary brasses, zinc is soluble in copper up to 37% and exhibits an all alpha phase; further increases in zinc results in the appearance of the second phase, beta.

• The two phases, alpha – ductile at room temperature, and beta – easily hot worked, is the key to wide range and unique fabrication properties of extruded brass. However the beta phase is particularly vulnerable to dezincification.

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• For maximum protection against dezincification, while still retaining the ease of fabrication, three factors have to be balanced to achieve the ideal structure with a minimum beta content.

• Careful control of time and temperature during manufacture,

which may include a special heat treatment.

• A slight increase in copper content to minimize the proportion of the beta phase

• The addition of a small amount of arsenic which implies protection to the alpha phase.

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Present Generation Dezincification Brass

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Stress Corrosion Cracking of Copper Alloys

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• The main cracking agent of copper and copper alloys is ammonia or its compounds.

• Other cracking agents mentioned in the literature include: – Acetates – Amines – Chlorates – Citrates – Mercury – Nitrates – Nitrites – Moist Sulfur Dioxide

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• No known tensile stress threshold • No known threshold ammonia concentration • Not sensitive to material strength • Stress-corrosion cracking occurs in a great variety of

brasses that differ widely in composition, degree of purity, and microstructure

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• Cracking occurs only in objects that are subjected to external or internal stresses

• Visible corrosion is frequently associated with the effect, but the corrosion may often be superficial

• Sufficient and continuous coatings of a metal, such as nickel, confer complete protection.

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• Cracks often follow an intercrystalline path • Traces of NH3 in the environment are an important agent in

inducing SCC in atmospheric exposure • Ammonia has a specific and selective action on the material

in the grain boundaries of brass • Highly stressed articles may be kept for years in a clean air

atmosphere without developing cracks • Ammonia and ammonium salts induce cracking • Surface defects which localize stresses, do not appear to

contribute to the development of cracks in the absence of an essential corroding agent, such as NH3.

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• Cracking always begins in surface layers that are under tension

• The behavior of a copper alloy subjected to the combined effect of tensile stress and NH3 is an index of susceptibility to SCC

• Susceptibility to SCC diminishes as the copper content of the brass is increased

• Protracted heating of 70Cu-30Zn brass at 100 °C (212 °F) does not develop cracks and does not reduce the internal stress appreciably

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Relative ranking of copper alloys susceptibility to ammonia SCC.

H26087 81


Case History 1

SCC of Copper Alloy C44300 (Arsenical Admiralty)

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Case History 1 – SCC

• Background – In service for ~ four years – Repetitive failures – Cooling water treated with amines

• Environmental Conditions – Stab-in bundle In a recirculating water cooling tower – OD exposed to cooling water – ID exposed to ethane/propane at 450 psig and 100F

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Case History 1 – SCC As-received tube samples

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Case History 1 – Split with dent

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Case History 1 – Close-up of split

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Case history 1 – Microstructure with crack

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Case History 1 – High mag view of crack

H24130-H25036-H25136-H26036-H26058

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Case History 2 – Dezincification

Case History 2

Dezincification Study of Different Brasses

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Case History 2 – Dezincification of Brass

• Switches monitor (detect) flow in municipal or well water • Potable waters of various quality • High temperatures 180F-190F when flowing

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• Merinque deposits in switch contained:

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• Client tried electroless nickel (EN) coating the switches

Machined hole area Internal as-cast body interior

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EN coated switch

showing merinque

dezincification

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• Client tested four different alloys to ISO 6509 – Determination of Dezincification Resistance of Brass – Alloy A – C83600 (CuZn5Sn5Pb5) – Alloy B (DZR) – CW602N (CuZn36Pb2As) – Alloy C – C85800 (CuZn40Sn1Pb1) – Alloy D – Red Brass (CuZn15) – Alloy E – Generic, hardware store yellow (DZR heat

treated, no As) brass

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ISO 6509 – Determination of Dezincification Resistance of Brass

• Exposure to 1% copper (II) chloride solution followed by microscopic examination.

• Temperature at 75F • Immerse samples for 24 hours • Microscopically observe for dezincification

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ISO 6509 Test Apparatus

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ISO 6509 Test Sample

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Case History 2 – Alloy A ISO 6509 Result

C83600 - No dezincification

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Case History 2 – Alloy B ISO 6509 Result

C35300 (DZR) - Minor dezincification

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Case History 2 – Alloy C ISO 6509 Result

C85800 Major dezincification

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Case History 2 – Alloy D ISO 6509 Result

C83600 (Red brass) - No dezincification

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Case History 2 – Alloy E ISO 6509 Result

Generic hardware store yellow DZR brass- Major dezincification

H2056 102

Case History 3 – Erosion-Corrosion

Case History 3

Erosion-Corrosion of Copper Tubing in a Recirculating Hot Water Loop

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• Background/Process – Hot water system in a 5-star resort – Hot water was in a pumped, recirculating loop – Water temperature >140F (for brief period) – Failures due to pin-hole perforation – Failures began ~1 year after service, accelerated ~3-4

years after start-up. – System included a Byron indirect water boiler, cement

lined storage tanks, and a T&S exchanger.

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• Water source and quality – Aquifer water – Water low in hardness, low in chlorides, low in pH (5.8-

6.2) and significant dissolved gases (DO and CO2). – Negative to slightly positive Langelier Index. – No chlorination or fluorination.

• ID corrosion products – Cu2O, CuO, CuCO3.Cu(OH2), (assumed from elemental

species).

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106


107


H2244 108

Case History 4 – Type I (Cold Water) Pitting Corrosion

Case History 4

Type I (Cold Water) Pitting Corrosion of Enhanced C12220 Copper Tubes in Air-

Conditioning Chiller Service

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• Background: – Air-conditioning Chiller using B359 C12220 copper tubes – Tubes have integral (enhanced) heat transfer fins on the

OD – ID contained cooling water on the tube side – OD contained HCFC 123 refrigerant on the shell side – Tubes failed due to ID perforation after < 1.5 years

service

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• Process Conditions – Tube side softened (well) water mixed with DI water

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• Red ID Deposits Green ID Deposits – O = 0.83% 3.57% – Si = 0.14 0.64 – S = 0.10 4.17 – Fe = 0.18 1.44 – Cu = 98.75 86.27 – Al 0.12 – Cl 1.25 – Ca 2.02

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ID pit and pit deposits

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• Summary Conclusions – Tubes experienced Type I pitting corrosion – Mitigating water chemistry

• Well water • High sulfate-to-chloride ratio • High residual chlorine (>3 ppm) • High suspended solids (erosive)

H23060 115

Case History 5 – Copper Tube Corrosion due to Exposure to Ammonia

Case History 5 Uniform corrosion of ASTM copper tubing in an a

S&T air dryer near an animal waste plant

116


• Background – Shell and Tube (S&T) Air Dryer experiencing repetitive

failure of B88 Type K copper tubes – Moisture saturated compressed air on TS (100F-38F) – Refrigerant on the SS – Tube failures were on the ID (air side) – Air intake near a pit containing animal waste products – pH of condensed water >8

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As-received exchanger tubes

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Exchanger manifold

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Close-up of exchanger manifold showing “rivulet” corrosion

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Exchanger tube ID showing general corrosion

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The End

corrosion of copper and copper alloys in potable water systems

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