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2-Phosphonobutane-1,2,4-tricarboxylic acid (PBTC) is an antiscalant that is widely used in reverse osmosis (RO) systems. Because of its high concentration in RO concentrate, eutrophication risk and anti-precipitation properties may affect subsequent treatments, therefore treatment strategies are needed to eliminate such substances.

2-Phosphonobutane -1,2,4-Tricarboxylic Acid (PBTC)

PBTC has low content of phosphoric and structural features of both phosphoric acid and carboxylic acid group, which enable its excellent scale and corrosion inhibition properties. Its antiscale property under high temperature is far better than that of organophosphines. It can improve zinc salt solubility, has good chlorine oxidation tolerance and good composite synergy.

CAS No.37971-36-1; Chemical Name:2-Phosphonobutane-1,2,4-tricarboxylic acid; PBTC;PBTCA;2-Phosphonobutane-1;scale inhibitor PBTCA;PHOSPHONOBUTANETRICARBOXYLIC ACID;2-Phosphonobutane-1,2,4-TricarboxyL;2-Phosphonobutan-1,2,4-tricarbonsure;2-phosphono-1,2,4-butanetricarboxylic;3-Carboxy-3-Phosphonohexanedioic Acid;2-Phosphonobutane-1,2,4-tricarbonicacid; 2-PHOSOPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID; 2-PHOSPHONOBUTANE-1,2,4-TRICARBOXYLIC ACID; 2-PHOSPHOBUTANE-1,2,4-TRICARBOXYLIC ACID; 2,4-Butanetricarboxylicacid,2-phosphono-1; PBTC; PBTCA; 2-phosphono-1,2,4-butanetricarboxylic; -Phosphono-1,2,4-butanetricarboxylicacid; 2-phosphono-1,2,4-butanetricarboxylic acid; aqueous 2-Phosphonobutane-1,2,4-tricarbonicacid; 2-Phosphonobutan-1,2,4-tricarbonsure; 4-butanetricarboxylicacid,2-phosphono-2; PHOSPHONOBUTANETRICARBOXYLIC ACID; 1,2,4-Butanetricarboxylic acid, 2-phosphono-scale inhibitor PBTCA; 2-Phosphono-1,2,4-butantricarboxylic acid(PBTC); 2-Phosphonobutane-1,2,4-tricarboxylic Acid (ca. 50% in Water); PBTC(2-Phosphonobutane-1,2,4-tricarboxylicacid); 3-Carboxy-3-Phosphonohexanedioic Acid; 2-Phosphonobutane-1,2,4-tricarboxylic acid ; PBTC; Phosphonobutane-1,2,4-Tricarboxylic Acid; 3-Carboxy-3-phosphonohexanedioic Acid;PBTC; 2-Phosphonobutane -1,2,4-tricarboxylic acid, 50% in water; 2-Phosphonobutane-12-Phosphonobutane-1,2,4-tricarboxylic acid (50% Aqueous solution)Inhibitor 2-Phosphonobutane -1,2,4-Tricarboxylic Acid; PBTCA; 2-Phosphonobutane-1,2,4-TricarboxyL37971-36-137971-63-1; C7H11O9P; Phosphonate antiscalant; Water treatment; Industrial/Fine Chemicals

PBTC is a high efficient agent as scale and corrosion inhibitor. PBTCA is the excellent stabilizer for zinc salt. It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. PBTCA can be used in situations of high temperature, high hardness, high alkali and high concentration index. In lavation fields, it is used as chelating agent and metal detergent.
PBTC is usually used together with zinc salt, copolymer, organophosphine, imidazole and other water treatment agents. When used alone, the dosage of 5-15mg/l is preferred.

Package and Storage: 200L plastic drum,IBC(1000L),customers’ requirement. Storage for one year in shady room and dry place.

Safety Protection:
Acidity, Avoid contact with eye and skin, once contacted, flush with water.

PBTCA;PBTC;PHOSPHONOBUTANE TRICARBOXYLIC ACID;2-Phosphonobutane -1,2,4-Tricarboxylic Acid;2-Phosphonobutane-1,2,4-tricarboxylic acid PBTC;

Water Treatment chemical PBTCA, a good corrosion inhibitors, is widely used in circulating cool water system and oilfield water injection system antifouling treatment.
Water Treatment chemical PBTCA is used as a corrosion inhibitor for industrial water treatment. This product has excellent complexing ability with Ca2 +, Zn2 +, Cu2 +, Mg2 +. The suitable PH range is from 7.0 to 9.5. Itcan operate at high temperature, high hardness, and high alkalinity conditions. It allows coolingwater concentration factor increased to seven or more.

Appearance: Colorless or Light Yellow Transparent Liquid
Active Acid (PBTCA): % 50.0 Min
Phosphorous Acid (as PO33-): % 0.5Max
Phosphoric Acid (as PO43- ): % 0.5Max
Density (20°C) g/cm3 : 1.25 min
PH (1% Water Solution):2.0 max

Application: Water Treatment chemical PBTCA is a high efficient agent as scale and corrosion inhibitor. It is the excellent stabilizer for zinc salt. It is widely used in circulating cool water system and oilfield refill water system as scale and corrosion inhibitor, suitable to composite with zinc salt and copolymer. It can be used in situationsof high temperature, high hardness, high alkali and high conc-entration index. In lavation fields, it isused as chelating agent and metal detergent. Water Treatment chemical PBTCA is usually used together with zinc, salt,copolymer, organophosphine, imidazole and other water treatment agents. When used alone, the dosage of 5-15mg/L is preferred.

2-phosphonobutane-1,2,4-tricarboxylic acid
EC / List no.: 253-733-5
CAS no.: 37971-36-1
Mol. formula: C7H11O9P

PBTC; PBTCA; (Phosphonobutane Tricarboxylic Acid 50%)
Phosphonobutane tricarboxylic acid is excellent as both antiscalants and corrosion inhibitors, because of its structural feature of carboxylic acid and phosphoric acid. The PBTC chemical is stable and high efficiency in the condition of high hardness, temperature, pH value, and indexed matter concentration.

While usually building with other organophosphates, PBTC acid also widely works together with zinc salts whose solubility it will increase. Phosphonobutane tricarboxylic acid can improve zinc salt solubility. PBTC 50% also have a higher tolerance to oxidation agents like chlorine or bromine in the system.

The first reaction for PBTC 50% production is between dialkyl phosphite (usually dimethyl phosphate in China) and maleic acid dimethyl ester under basic catalyst. Tetraalkyl ester of phosphonosuccinic acid forms and immediately reacted with methyl acrylate. The following thereupon saponification yields PBTC.

CAS No.: 37971-36-1, from ChemIDplus, EPA Chemicals under the TSCA, EPA DSStox, European Chemicals Agency (ECHA). 40372-66-5, from ChemIDplus, European Chemicals Agency (ECHA).

EC No.: 253-733-5, from the European Chemicals Agency (ECHA). 254-894-4, from the European Chemicals Agency (ECHA).

Molecular Formula: C7H11O9P

As an excellent inhibitor to both scale and corrosion, PBTC 50% is an excellent stabilizer for zinc salt. It is widely applied in the refilling system and circulated cooling system for oil fields, steel mills, and mines. PBTC 50 can be used in situations of high temperature, high hardness, high alkali, and high concentration index.

Besides, phosphonobutane tricarboxylic acid is used to chelate metal ions in lavation and detergent industries as metal detergent. In pH 7-10, 5-15 mg/L is recommended if only PBTC acid. PBTC 50% is usually used together with the zinc salt, copolymer, organophosphine, imidazole, and other water treatment agents. When used alone, the dosage of 5-15 mg/L is preferred.

Molecular Weight: 270.13
1,2,4-Butanetricarboxylic acid, 2-phosphono
1,2,4-Butanetricarboxylic acid, 2-phosphono-
2-Phosphono-1,2,4 butanetricarboxylic acid
2-Phosphono-1,2,4-butanetricarboxylic acid (aerosol), as PBTC
2-phosphono-1,2,4-butanetricarboxylic acid; 2-phosphonobutane-1,2,4-tricarboxylic acid; Dequest 7000
2-Phosphonobutane-1,2,4-tricaboxylic acid
2-phosphonobutane-1,2,4-tricarboxylic acid
2-Phosphonobutane-1,2,4-tricarboxylic acid, >5% in a non hazardous diluent
3-Carboxy-3-phosphonohexanedioic acid
Phosponobutane tricarboxylic acid (PBTCA)

IUPAC names
2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC)

Trade names
Aquacid 101EX
PBTCA (AM) (50% aqueous solution)
Uniphos 100

Other identifiers
CAS number: 94386-13-7
1,2,4-Butanetricarboxylic acid, 2-phosphono-
2-Phosphono-1,2,4-butanetricarboxylic acid
2-Phosophonobutane-1,2,4-tricarboxylic acid
2-Phosphonobutane-1,2,4-tricarbonic acid
EINECS 253-733-5
phosphonobutanetricarboxylic acid
2-Phosphono butane-1,2,4-tricarboxylic acid
EC 253-733-5
3-Carboxy-3-phosphonohexanedioic Acid
Butanetricarboxylic acid, 2-phosphono-1,2,4-
(S)-2-phosphonobutane-1,2,4-tricarboxylic acid
2-Phosphonobutane-1,2,4-tricarboxylic acid 50% in water
2- Phosphonobutane -1,2,4-tricarboxylic acid, tetra sodium salt
2-Phosphonobutane-1,2,4-tricarboxylic acid(50% Aqueous solution)
CAS No. 37971-36-1
EC No. n/a
Synonyms 1,2,4-Butanetricarboxylic acid; 2-phosphono-; 2-Phosphono-1,2,4-butanetricarboxylic acid; 2-Phosphonobutane-1,2,4-tricarbonic acid; 1,2,4-tricarboxylic acid; Butanetricarboxylic acid

2-Phosphonobutane-1,2,4,-tricarboxylic acid (PBTC)
​2-Phosphonobutane-1,2,4,-tricarboxylic Acid (PBTC) is a very effective scale inhibitor used in various industrial applications. Due to its higher performance properties it is a very cost effective inhibitor compared to standard Phosphonates such as HEDP/ATMP. This is mainly due to superior stability to chlorine, bleach and bromine. In cooling water PBTC performs well at high PH or temperatures. It further shows high effectiveness in high alkaline solutions such as industrial cleaners.

Cooling water systems / industrial water treatment
Industrial detergents
Liquid dishwashing concentrates
Metal surface treatment as corrosion inhibitor for steel
Retardant in concrete
Sequestering agent in textile auxiliaries

(S)-2-phosphonobutane-1,2,4-tricarboxylic acid; 1,2,4-Butanetricarboxylic acid, 2-phosphono-1,2,4-Butanetricarboxylic acid,2-phosphono-2- Phosphonobutane -1,2,4-tricarboxylic acid, tetra sodium salt2-Butanephosphate-1,2,4-tricarboxylic acid (PBTC)2-Phosophonobutane-1,2,4-tricarboxylic acid2-Phosphono butane-1,2,4-tricarboxylic acid2-Phosphono-1,2,4-butanetricarboxylic acid2-Phosphonobutane -1,2,4-Tricarboxylic Acid2-Phosphonobutane 1,2,4-tricarboxylic acid (PBTC)2-Phosphonobutane-1,2,4-tricarbonic acid2-Phosphonobutane-1,2,4-tricarboxylic acid (ca. 50% in water)2-Phosphonobutane-1,2,4-Tricarboxylic acid [PBTCA]2-Phosphonobutane-1,2,4-tricarboxylic acid 50% in water2-Phosphonobutane-1,2,4-Tricarboxylic Acid(PBTCA)37971-36-13-Carboxy-3-phosphonohexanedioic Acid

PBTCA is an aqueous solution of PBTC for water treatment and cleaning agents.  PBTCA AM can be used in water treatment applications as an effective scale inhibitor in cooling water circuits and process water systems.  In addition, PBTCA AM is also an excellent corrosion inhibitor for carbon steel.  PBTCA AM is most effective at neutral to high pH and high hardness, also making it an effective dispersing agent for alkaline cleaning agents and detergents.  PBTCA AM has outstanding solubility, and can be mixed with strong acid or alkali solutions.

Corrosion Inhibitor
Household, Industrial and Institutional Cleaners
Water Treatment
Market Segments:
Industrial Cleaners and Degreasers
Institutional Cleaners and Degreasers
Municipal Wastewater Treatment


PBTC is a highly effective scale and corrosion inhibitor, which active ingredient
PBTC was developed by the Bayer AG. Main field of application are the treatment of cooling and process water as well as the area of cleaning formulations.
Chemical name PBTC is a 50 % solution of 2-Phosphonobutane-1,2,4-tricarboxylic acid (abbreviation: PBTC) in water
CAS Reg. No. 37971-36-1
Empirical formula C7H11O9P
Molecular weight 270.13 g/mol
Physical form clear, colorless to yellowish, low-viscous,almost odorless liquid
Health and safety information Safety data and precautions which must be observed under all circumstances are to be found in EU Safety Data Sheet No. 000969.

Active agent content 50 ± 1 % by mass 2022-2303301-00D Orthophosphate content (as PO43-) ≤ 0.2 % by mass 2022-2303601-00D
Density at 20 °C : 1.285 ± 0.015 g / cm³ DIN 51 757
Turbidity ≤ 10 NTU (= TE/F) DIN 38 404, part 2
Gardner color ≤ 2 - DIN 53 995
Hazen color (at dispatch) ≤ 100 (APHA) ISO 6271
Additional Information
Property Typical Value Unit Test Method
PBTC share *) ca. 84 mol-% 2012-0567802-00D
31P-NMR spectroscopy
Viscosity at 20 °C 17.5 ± 7.5 mPa .s DIN 53 015
Refractive index at 20 °C (n20D) :1.417 - DIN 53 491
pH value of the aqueous solution with 2 % PBTCA:  1.6 ± 0.1 - DIN 38 404, part 5
Iron (as Fe): ca. 5 mg / l AC-F/V/246/03/88
Total chlorine (as Cl): ca. 4 mg / l 2011-0380801-93D
Hazen color (ex works) :10 (APHA) ISO 6271*) referred to phosphorus compounds
These material properties are typical properties and, unless specifically indicated otherwise, are not to be considered as delivery specification.
product data sheet: PBTCA

ISO tank container
1250 kg IBC container
250 kg polyethylene drum
The product can be stored in tightly sealed original packaging without a deterioration of quality for a period of at least two years in case of appropriate storage. Material which
has solidified on account of cold (solidifying point approx. – 15 ° C) can be defrosted without a reduction of quality.
The following materials have proved suitable for the metering tanks, pumps and lines for
PBTC: glass, stainless steel (e.g. DIN W1.4571 = US AISI 316 TI), plastics such as polyethylene, polytetrafluoro ethylene (PTFE) and polyvinyl chloride (PVC). Seals should
be made form PTFE or graphite.
No labeling is required for PBTCA under Germany’s regulations on hazardous substances and the equivalent EU Directives.
PBTC - effects
Scale inhibition
PBTC has proved highly effective as a threshold inhibitor. Very low additions (ppm range), i.e. in far less than sub-stoichiometric concentrations (calculated on the
hardness of the water), prevent the formation of scale and incrustations, respectively. Even water which is highly over-saturated with hardness constituents such as calcium
carbonate remain without scale when PBTC is added. The outstanding effectiveness of PBTCA is proofed by a multitude of practically orientated trials, which can be discussed
and are available. Dispersion The adsorption of the PBTC anion on inorganic particles suspended in water results in a negative charge on their surfaces and thus in an improvement in
dispersibility. This is why neutralized
PBTC is used as a dispersion agent /deflocculation agent for inorganic slurries and slips.
Corrosion inhibition: Under the conditions found in cooling water,
PBTC is a good corrosion inhibitor for carbon steel. In the case of relatively soft water, it is common to combine PBTCA® with synergistic substances (phosphates,
zinc salts). In water of higher hardness or with sufficiently high alkalinity (approx. 300 mg/l or more, calculated as calcium carbonate), formulations containing PBTCA®
and no inorganic components – known as all-organic formulations – are highly effective. In alkaline cleaning agents, the corrosion-inhibiting effects of PBTCA® on
aluminium can be a benefit.

PBTC - properties
PBTC can be mixed in any ratio with water. It is soluble in lyes, e.g. sodium hydroxide solution, and in acids, e.g. sulfuric acid. Because of its outstanding solubility,
even formulations which already contain high concentrations of other active substances can be optimized by the addition of PBTCA.
PBTC is a strong acid. When it is mixed with alkali, a heat of neutralization of around 210 kJ (approx. 50 kcal) is released per mole PBTC. This is why the final
temperature of a solution produced without cooling by neutralizing PBTCA®  AM (commercial product) with 20 % sodium hydroxide solution is around 50 °C higher
than the temperature of the starting solutions. If higher concentrations of sodium hydroxide are used, it must be expected that the solution will begin to boil if it is not
cooled. The safety precautions which normally apply for acid-base neutralization must therefore be observed when mixing PBTCA commercial product with concentrated sodium hydroxide solution.
Stability to hydrolysis
PBTCA can be used in aqueous solutions, lyes and acids up to temperatures considerably above 100 °C. Investigations of the stability have shown that, for example,
the half-life (50 % degradation to orthophosphate) in process water with a pH of 9 and a temperature of 200 °C is around 20 hours.
Inhibitor loss / turbidity region When combined with polyvalent cations, threshold inhibitors can form poorly soluble salts which, when they exceed the solubility
limits, often result in turbidity. Field experience and special trials have shown that the tendency of the inhibitor to precipitate caused by, for example, Ca2+ and
Fe(III) is much lower in PBTCA® than in other phosphonates. For this reason, inhibitor losses are low when PBTCA® is used. 
 Fig. 1: Tendency of the phosphonates to form undissolved calcium salts
0 5 10 15 20
phosphonate start content [mg/l]
residual phosphonate content [%]
Ca2+ concentration = 200 mg/l
pH: 8.5 temperature: 60°C storage time: 24 h
product data sheet: PBTCA

Stability to chlorine, bleaching lye and other oxidizing agents Because of its outstanding stability to chlorine and bleaching lye, PBTCA® is often used together with bleaching lye in
disinfectant alkaline cleaning agents. When manufacturing formulations which contain PBTCA, alkali and bleaching lye, PBTCA must always be neutralized before addition of the latter. Like all acids, acidic PBTCA generates toxic chlorine gas when mixed
with bleaching lye. Under cooling water conditions (neutral to slightly alkaline environment), the high stability of PBTC to chlorine and hypochlorite is also not matched by most other phosphonates. The product also has outstanding stability to bromine and hypobromite which are generated by adding
chlorine to bromide. Bromine does not affect PBTC even after many hours but destroys HEDP, for example very quickly (cp. fig. 2). Unlike aminomethylene phosphonates such as ATMP or DTPMP, PBTC is also stable under operating conditions to chlorine dioxide, which is used to prevent reinfection in bottle-washing plants.
 Fig. 2: Stability of phosphonates to chlorine and bromine
Conditions for test a):
total hardness SE = 3.0 mmol/l (300 mg/l as CaCO3); total alkalinity KS 4.3 = 3.2 mmol/l (160 mg/l as CaCO3);
start pH = 8.5; storage temperature 60°C
phosphonate concentration: 10 mg/l; chlorine concentration (as bleaching lye): 10 mg/l
Conditions for parallel test b):
as in a) plus 1 mg/l bromide
The residual phosphonate concentration was calculated from the analytical determined orthophosphate
time [h]
residual phosphonate content [%]
PBTC a) b)

PBTCA - ecology and toxicology
Bacteria which degrade PBTCA® were isolated from natural sources (activated sludge, river water and river sediment).
Degradation is rapid if a second carbon source is available to the bacteria and inorganic phosphate is present in concentrations of just a few mg/l.
In pond water, biodegradation was found to take place under natural conditions without isolation and adaptation of the bacterial population. The half-life was 28 days. Only
0.3 % of radioactively marked PBTC could still be found in the water after 208 days. In contrast, in biodegradability tests using standard methods (e.g. OECD 301 D, 302
B), PBTC was found to be not easily degradable. Degradation by light In water, PBTC is degraded by light. The rate of degradation depends on the intensity
of the light and on the other constituents in the natural water. In the presence of traces of iron or nitrate, the half-life of PBTC is just a few hours.
Adsorption on activated sludge and sediment Trials have shown that more than 95% of PBTC is adsorbed by activated sludge. If the water treatment plant has a third treatment
stage (phosphate precipitation with aluminium or iron (III) salts) PBTC residues are also precipitated with the consequence that the discharge from the waste water
treatment plant contains virtually no PBTC. PBTC is eliminated from standing water over
resting sediment through adsorption on the sediment with a half-life of five days. If the sediment is kept in suspension, the adsorption process is much quicker (half-life
of just a few hours). Complex formation PBTC is a much weaker complexing agent than EDTA. There is no reason to expect a remobilization of heavy metals from
sediment by PBTC. This has been confirmed by laboratory trials.
Trials have shown that PBTC has no harmful effect on aquatic organisms (fish, daphnia, algae, bacteria) or on terrestrial organisms (Earthworms) and sediment organisms (midge larvae).

product data sheet: PBS AM

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