21/06/2018

1. Metallic Materials

Several types of corrosion exist, each capable of producing a multitude of various types of damage, and consequently resulting in several different potential hazards. While a more even surface attack is easily recognisable and measurable, cracks, holes, internal fractures, and brittleness, pose a much more dangerous problem. The resulting leakages, breaks, and bursting events represent types of damage, which depending on the rate of energy release, emission of toxins, and the presence of flammable or explosive materials can represent a significant treat not only to human lives, but also to the environment. The first step in protection against corrosion is therefore the selection of an appropriate corrosion-resistant material for exposure to a specific medium.

Corrosion resistance isn’t a property of a material, rather a type of behaviour, of the material, in which an interaction takes affect between the surface of the material and the surrounding medium.

The resistance data of the most frequently used metallic materials in the construction of receptacles can be found in BAM’s Databank of dangerous goods. A large portion of this Data is published in:

BAM List (Requirements for tanks for the carriage of dangerous goods)
Dangerous Goods Database
Evaluation of the resistance of metallic receptacle materials and Polymer seals, coatings, and lining materials (PDF is available in german only )

The following metallic materials are included in the evaluation:

1.1 Unalloyed Steel

This type of steel contains a maximum alloy content of 5% of the weight. The desired properties of steel, such as sturdiness, notch impact strength, weldability, hardness, and deformability etc. are maintained within a mixture of up to this level. The corrosion resistance of unalloyed steel is clearly rated as lower to that of alloyed steel.

Some properties of unalloyed steels, for which specific conditions of the resistance evaluation can be met, are listed in the following table.

The resistance assessment of unalloyed steels:

Steel TypeMaterial No.Rating
S235JRG11.0036DIN EN 10 025
S235JR1.0037DIN EN 10 025
S235JRG21.0038DIN EN 10 025
S235J2G31.0116DIN EN 10 025
S275J2G31.0144DIN EN 10 025
P235GH1.0345DIN EN 10 028-1 DIN EN 10 028-2
P265GH1.0425DIN EN 10 028-1 DIN EN 10 028-2
P295GH1.0481DIN EN 10 028-1 DIN EN 10 028-2

1.2 Austenitic CrNi- and CrNiMo- Steel

The best known and most frequently used austenitic steels belong to the two Alloy groups with a composition of 18% chromium and 8% nickel (CrNi- Steel), and 17% chromium, 12% Nickel, and 2-3% Molybdenum (CrNiMo- Steel). Within both steel groups are different materials, which differ from one another in their carbon content (e.g. 1.4301 and 1.4306, 1.4401 and 1.4404), are characterised by a stabilisation with titanium or niobium (e.g. 1.4541, 1.4571), or are nitrogen-alloyed (e.g. 1.4311, 1.4406).

New materials with an increased level of corrosion resistance are developed by starting with these standard austenitic steels and increasing the alloy content of chromium, molybdenum, nickel, and also partly of nitrogen, copper, and manganese (e.g. the steels 1.4439, 1.4529, and 1.4562). Although in contact with certain mediums these steels have a higher level of corrosion resistance than standard austenitic steels, the corrosion resistance evaluations of the listed materials can also be applied to them.

Materials Resistance Evaluation of Standard Austenitic Steels:

Material No.DIN-LabelChemical Composition: Mass Fraction [%]
CCrNiMoCuNOther
1.4306X2CrNi19-110.0218.210.1--0.14-
1.4541X6CrNi18-100.0417.39.1--0.01Ti
1.4401X5CrNiMo17-12-20.0317.110.72.1-0.03-
1.4404X2CrNiMo17-12-20.0217.311.12.2-0.04-
1.4406X2CrNiMoN17-11-20.0217.210.32.1-0.14-
1.4571X6CrNiMoTi17-12-20.0416.810.92.1-0.01Ti

1.3 Austenitic Stainless Steel

So called "Super Austenitic Steels" with a high chromium (20-25%), molybdenum (4-7%) and nitrogen (0,2-0,5%) content were developed for use with corrosive dangerous goods. To maintain the austenitic grain of these materials a nickel content of 18-28% is required. When developing this steel the combination of Chromium, Molybdenum, and Nitrogen is chosen so as to optimise the Pitting Resistance Equivalent number (PRE), thus increasing the Pitting Resistance of the steel. Nickel and molybdenum serve to increase the resistance to stress cracking, while the nitrogen has a positive affect on the mechanical properties and the thermal stability.

The stainless steel 1.4529 is used in uncomplicated cellulose equipment for the handling of sea water (in for example: sea water heat exchangers, or sea water desalination plants), or in flue gas desulphurisation with organic chemicals and synthetic rubbers.

The "Super Austenitic Steel" 1.4562 introduced in 1989 has approximately a 6% higher Nickel and Chromium content compared to the material 1.4529, and exhibits a very good level of corrosion resistance in both reducing and oxidising mediums. This material has proven itself in the manufacture of phosphoric acid through wet processes, in which several impurities, such as chlorine, fluorides, and oxidising metal ions can be found in varying concentrations in the raw materials (depending on their source). The "Super Austenitic Steel" was used in the paper and cellulose industry, the production of sulphuric acid, the reprocessing of spent sulphuric acid, flue gas cleaning, fibre-production, offshore technology, and Hydrometallurgy. Tank containers and street tank vehicles composed of this material for the transport of dangerous goods are examples of the wide variety of possible applications of this material.

The corrosion resistance of the two stainless steels 1.4529 and 1.4562 to corrosive dangerous goods was extensively and successfully tested within the scope of a research project.

1.4 Nickel-Chromium-Molybdenum-Alloys

Nickel-Chromium-Molybdenum-Alloys are termed C-Alloys. The material 2.4605 demonstrates the optimal combination of versatile corrosion resistance and processability out of the C Alloys. Apart from the alloyed components Nickel (59%), Chromium (23%), and Molybdenum (16%), no other elements such as Wolfram or Iron are present. These materials demonstrate a very high level of resistance to mineral acids, organic acids, and mixed acids, also when they are impure. C Alloys are employed in the manufacture of various organic products (Polycarbonates, Polyethylene terephthalate, acidic acids etc.), the fabrication of liquid acids, the extraction of oil and Gas under acidic gaseous conditions, the production of chlorine and fluoride chemicals, and waste incineration.

The corrosive resistance of the nickel based alloy 2.4605 when dealing with corrosive dangerous goods was extensively and successfully tested within the scope of a research project.

1.5 Aluminium and Aluminium Alloys

The materials resistance evaluations of substances composing of at least 99.5% Aluminium (EN AW-1050A) are also applicable in the cases of Alloys with improved strength properties, like for example the alloy AlMg4.5Mn (EN AW-5083) often used in Tank construction. Due to their high level of corrosion resistance these Alloys are counted among the so called Sea Water Suitable Aluminium Materials. Aluminium and aluminium alloys only succumb to surface corrosion when exposed to a pH either lower than 4.5 or higher than 8.5. The pitting corrosion potentials of the various aluminium materials do not differ substantially from one another.

1.6 Zinc (Coating metal in the manufacture of galvanised steel Receptacles)

Zinc is a base metal. Therefore if electrolytic corrosion occurs zinc is actively dissolved. The disintegration of zinc can be inhibited through the application of a protective coating, which still allows the high level of corrosion resistance of the zinc layer to take effect in neutral mediums. Zinc is applied (by means of hot-galvanising) as a coating metal in the manufacture of galvanised Receptacles / Tanks.

The assessment of the resistance is based on:

a) Literature References
b) Experience
c) Laboratory Experiments

Unless otherwise stated, for example with melting mediums, the materials resistance evaluation is valid for an average operating temperature of up to a maximum of 30°C, although short term warming is permitted up to a temperature of 50°C.

Although no specific requirements for the purity of the mediums exist, the materials resistance evaluation is only valid for standard technically pure materials. Under no circumstances is it valid for waste or a mixture consisting of an unknown quantity and concentration of impurities or other constituents. The corrosion resistance of waste or mixtures is determined through a corrosion experiment.

2. Polymer Receptacles, Sealants and Coating Materials

The resistance of Polymer Materials to the effects of chemicals is dependent on the chemical composition and structure of the material, the composition and quantity of the filling material and aggregate, the composition of the acting medium, and the conditions under which it takes effect. Depending on the type of exposure the medium can be assigned to one of two groups:

  • Physically active Mediums: Do not react with the Polymer, but can cause swelling to the point of disintegration, and cause reversible changes to the properties through destruction of the molecular-bonds in the Polymer Material.
  • Chemically active Mediums: React with Polymers and irreversibly alter their properties. It is characteristic of chemical degradation of a Polymer that even a negligible chemical alteration can significantly alter the physical properties of the material.

When in an aggressive medium Polymers are exposed to a mechanical stress. This mechanical tension alone is enough to destroy the covalent bonds in macromolecules, or possibly also activate the molecules. Since during most practical applications a Polymer could experience both mechanical and chemical stress simultaneously, one must pay attention to the various resulting occurrences, such as: Chemical Relaxation, Creep Behaviour, the Behaviour of Alternating Cyclic Stress, and Stress Cracking. The Creep Strength, the behaviour of long-term mechanical stress is a characteristic of practical applications of Polymers; as such applications tend to displace the molecular structure even at room temperature. These Creep / Flow properties can be strongly influenced as a time and temperature dependent process by the concurrent effects of chemical substances.

To make the estimation of the attack of a medium easier it’s helpful to divide the chemical substances into the following:

  • Inorganic substances like water, salt and salt solutions, acids, alkali and gases.
  • Organic substances belonging to those classified as solvents.
  • Other substances whose constituents don’t fall into one of the previously mentioned two categories.

The following statements can be made in relation to the various groups:

a) Water and Inorganic Substances
If neither moistening (and thus no solvation) nor a strong chemical attack occurs, a high level of resistance with only negligible alterations to the properties can be expected. The temperature and concentration determine the aggressiveness. Solid undissolved substances rarely result in an attack.

b) Organic Substances
A chemical attack occurs very seldom during exposure to an organic substance, but a more or less large solvation occurs almost always. Hydrophobic materials are attacked by hydrophobic solvents. The stronger they are the more the structure and dipole-moment of the material and the solvent resemble one another.

c) Other Substances
No general statement can be made for this group in relation to their effect on various materials, as this group consists of a mixture of two or more different materials. If a single component dominates the mixture it is possible to make an estimation.

The resistance data of the most frequently used metallic materials in the construction of receptacles can be found in BAM’s Databank of dangerous goods. A large portion of this Data is published in:

BAM List (Requirements for tanks for the carriage of dangerous goods)
Dangerous Goods Database
Evaluation of the resistance of metallic receptacle materials and Polymer seals, coatings, and lining materials (PDF is available in german only)

Table: Overview of the resistance of rated polymer materials listed in the Databank DGG against chemicals.

PTFEPolytetrafluorethylene
FKMFluorcarbon Rubber
PFAPerfluoroalkoxyethylene
NBRButadien-Acrylonitrile-Rubber with 28 % Acrylonitrile in the Rubber
HNBRHydrogenated Nitrile Butadiene Rubber
NRNatural Rubber
IRIsoprene Rubber
IIRButyl Rubber
EPDMEthylene Propylene Diene Monomer
CRChloroprene Rubber
CSMChlorosulponated Polyethylene Rubber
SBRStyrene-Butadiene Rubber
ACMAcrylate Rubber
MFQFluorsilicone Rubber
MVQSilicone Rubber
ECTFEEthylene-Chlorotrifluoroethylene-Fluorocopolymer
AUPolyesterurethan
PEPolyethylene
PPPolypropylene
PVCPolyvinyl Chloride
PVDFPolyvinyliden Fluoride
PAPolyamide

The evaluation of the resistance is based on the following:

a) Litierature References
b) Experience
c) Laboratory Experiments

Whereas the resistance to chemically active mediums can be estimated through simple Immersion Experiments in a particular medium with similar or stronger impact conditions (an increase in the temperature, pressure, or current flow), the permeation, absorption, or resistance to Stress Cracking in the most cases involves a timely and extensive analysis.

Although visual assessments are made during the Immersion Experiments, discernable alterations in the weight and/or dimensions of the test object as well as any change to the mechanical characteristics or other physical properties in relation to the immersion time indicate the classification of the Evaluations class.

Frequently used Evaluations Classes in literature and company prospects include: proven, conditionally proven, and unproven. (beständig, bedingt beständig und unbeständig)

For assessing the resistance of elastomers to liquid mediums one should refer to the German Institute for Standardization DI ISO 1817: Elastomer – Determination of the reaction to liquid substances. This International Standard describes processes for determining the resistance of vulcanised elastomers against the effects of liquids, in which the change in mass, volume, dimensions, density, and stress-strain properties are measured before and after exposure to the test liquid.

In order to pass the evaluation the resistance of the Polymer must be demonstrated up to a temperature of 60 °C.

In contrast to the Materials Resistance Assessment of metallic materials this Resistance Evaluation only accounts for the effects of the filling goods on the polymer material. Since large fluctuations in the properties of the considered base materials can occur due to various cross linking factors, various filling goods and diluents, the resistance data of the polymer materials has certain orientating characteristics. For specific service conditions it is advised to conduct more specific trials.

3. Higher alloyed stainless steels and nickel based materials for tank construction

A large number of corrosive dangerous goods exist, including halogen-containing substances as well as oxidising and reducing acids, which call for materials with a higher level of corrosion resistance than those found in the BAM-List: - Tank requirements for the carriage of dangerous goods. Chloride-containing materials, and materials which form hydrochloric acid in a dissociated form in the presence of humidity, demonstrate a lack of corrosion to metallic materials only under dry conditions.

As such the tanks must be perfectly dryly filled and sealed tight in order to prevent any permeation of moisture from occurring during the filling and / or transporting of the goods. To ensure any start at corrosion is promptly detected the tanks must be subject to regular corrosion tests separated by short intervals.

To eliminate this danger of corrosion the lining of the tanks is replaced with polymer materials. The very resistant fully and partially fluorinated polymer materials (for example Polytetrafluoroethylene (PTFE), Perfluoralkoxy-copolymer (PFA), Fluorinated ethylene propylene (FEP), Ethylene Tetrafluoro Ethylene (ETFE), Polyvinylidene fluoride (PVDF) and Trifluorethylen-Ethylen-Copolymer) are presently used in the chemical industry.

Another alternative would be the use of high-alloyed stainless steel and nickel-based alloys. By increasing the chromium, nickel and molybdenum content of standard austenitic steels the resistance to strong acids and chloride based solutions can be improved. Additions of wolfram, titanium, nitrogen and copper also contribute to the improvement of corrosion resistance. Molybdenum is specifically used to augment the hole- and crevice-corrosion resistance. The highly alloyed rustproof austenitic steels 1.4529 and 1.4562 as well as the nickel-based alloy 2.4605 (see Table 1) were therefore assessed for potential use as wall materials in tanks for the transport of dangerous goods, within the scope of a ThyssenKrupp VDM GmbH financed research project in March 2002.

Presently only a limited number of results of the corrosion investigations of these materials with corrosive dangerous goods and water polluting substances are available. 6684 dangerous goods and water polluting materials are included in the 7-th edition of the BAM list. In order to obtain corrosion data of these three highly alloyed materials; the following corrosive materials were selected from the BAM-List for use in corrosion tests performed in the department group VII:3 of BAM (Dr. Bäßler) and in the Institute for Corrosion Protection Dresden Ltd. (IKS) with samples welded at 55 °C.

  1. Inorganic Halogenides
    Aluminium chloride, iron(III) chloride (ferric chloride), copper(II) chloride, sodium bromide, thionyl chloride, zinc chloride.
  2. Acidic Organic Halogenides and Halogen Hydrocarbons
    Acetyl chloride (ethanoyl chloride), chlorobenzyl chloride, choline chloride, diallyldimethyl ammonium chloride, epichlorohyrin, polyalluminium chloride, trioctyltin chloride.
  3. Halogen Carbonic Acids
    2-Chloropropionic Acid, monochloracetic acid, trichloroacetic acid,
  4. Chlorsilane
    Diphenyl Dichlorosilane, dimethyl dichlorsilane
  5. Chlorates, Perchlorates, Chlorites
    Barium chlorate, sodium perschlorate, sodium chlorite
  6. Hypo chlorites
    Sodium hypo chlorite
  7. Hydrogen Sulfates
    Potassium hydrosulfate , ammonium hydrogen sulphate
  8. Sulfides
    Sodium sulphide
  9. Sulphuric acid and nitrating acid mixture
  10. Hydrochloric and perchloric acid
  11. Sulphonic acid
    Chlorosulphonic acid, methanesulfonic acid
  12. Phosphoric acid and phosphorous acid

The selection of the materials to be tested is extended according to the results of the corrosion attempts.
Table: Composition of the materials 1.4529, 1.4562 und 2.4605 [in %]

MaterialCSNCrNiMnSiMoCuFePAlCo
Alloy 926
1.4529
0.0080.0020.1920.824.60.870.336.520.83R0.018
Alloy 31
1.4562
0.0090.0020.226.531.41.50.086.51.19R0.013
Alloy 59
2.4605
0.0040.003 22.7R0.150.0415.50.010.70.0030.20.03
SG-NiCr23Mo16
2.4607
r
0.015
r
0.015
 22-
24
Rr
0.5
r
0.08
15-
16.5
 r
1.5
r
0.02
0.1-
0.4
r
0.3

Based on the results of the corrosion attempts carried out up to now by BAM and IKS Dresden the following corrosion resistance assessments can be made:

  1. The nickel based alloy 2.4605 has the highest level of corrosion resistance of the three materials, and is resistant to contact with concentrated hydrochloric acid in all test substances at temperatures up to 55 °C.
  2. The „Super Austenitic Material“ 1.4562 is a very corrosion resistant material. Exceptions to the application of this material are made when dealing with hydrochloric acid and monochloracetic acid at 110 °C (when it turns liquid). In 90% of the cases dealing with 2-Chloropropionic acid and Chlorosulphonic acid the material 1.4562 can only be employed provided regular tests separated by short intervals are made on the tank-container. The application of this material is restricted to cases dealing with concentrated aluminium chloride, copper(II) chloride, and Iron(III) chloride solutions.
  3. The „Super Austenitic Material“ 1.4529 demonstrates the lowest level of resistance in comparison to the other two materials. It is not resistant to hydrochloric acid, perchloric acid, sodium chlorite, or Sodium hypo chlorite and is has only limited resistance in concentrations of aluminium chloride, copper(II) chloride, and Iron(III) chloride solutions. The material 1.4529 can only be used in saturated Chlorosulphonic acid provided regular tests separated by short intervals are made on the tank containers. It is worth noting that this material was not included in the entire transportation program

The materials 1.4529, 1.4562 and 2.4605 are consequently seen as a very good alternative to the internal tank linings for the transport of corrosive dangerous goods, as due to the high level of corrosion resistance demonstrated by these materials the repair costs of the internal coating can be omitted.

The results of this research project were published in the 8-th edition of the BAM list, and were introduced to the users (e.g. Tank manufacturers and operators) as well as to the corrosion experts [1-17]. The intensive publication of the results in written as well as verbal form led to the construction of six street tank-trucks and three tank containers from the material 1.4562 (see photo above) in 2004 and 2005.

[1] Bäßler, R.: Suitability of More Noble Materials for Tanks for Transport of Dangerous Goods, ACHEMA, 2003
[2] Weltschev, M.: Super Steels, Hazardous Cargo Bulletin, S.64-66, Oktober 2002
[3] Weltschev, M.: Einsatz von höherlegierten Sonderedelstählen und Nickelbasis­legierungen im Tankbau Gefahrgut-Technik-Tage Berlin - Innovative Tanktechnik, November 2002
[4] Weltschev, M.; Bäßler, R.: Höherlegieren gegen Korrodieren. Gefährliche Ladung 11 (2002), S.18-20, Hamburg: K.-O.Storck Verlag 2002
[5] Weltschev, M.; Bäßler, R.: Tankwerkstoffe für den Gefahrguttransport – Bewertung der Beständigkeit der „Superaustenite“ X1NiCrMoCuN25-20-7 und X1NiCrMoCu32-28-7 sowie der Nickellegierung NiCr23Mo16Al für den Tankbau. TÜ Bd. 44 (2003) Nr. 11/12
[6] Weltschev, M.; Bäßler, R.; Werner, H.; Behrens, R.: Suitability of high-alloyed metallic materials for the transport of dangerous goods, LOSS PREVENTION, Prag, 2004
[7] Weltschev, M.: Innovative korrosionsbeständige höherlegierte Tankwerkstoffe. Gefahrgut-Technik-Tage Berlin – Innovative Tanktechnik –, 25.-27. November Berlin, Tagungsband, S.52–60, 2004
[8] Weltschev, M.;Bäßler, R.; Werner, H.; Behrens, R.: Assessment of the corrosion resistance of high-alloyed metallic tank materials in the BAM-List – Requirements for Tanks for the Transport of Dangerous Goods, EUROCORR 2003 – The European Corrosion Congress, Budapest 2003
[9] Weltschev, M.; Bäßler, R.; Werner, H.; Behrens, R.: Suitability of More Noble Materials for Tanks for Transport of Dangerous Goods, CORROSION 2004, paper No 04228, NACE International, New Orleans, USA, 2004
[10] Weltschev, M.; Bäßler, R.; Werner, H.; Alves, H., Behrens, R.: Beständigkeitsbewertung von hochlegierten Werkstoffen für den Einsatz als Tankwandungswerkstoffe zum Transport von Gefahrgütern und wasserverunreinigenden Stoffen. Werkstoffwoche München, September 2004
[11] Bäßler, R.; Weltschev, M.; Werner, H.; Alves, H., Behrens, R.: Evaluation of the corrosion resistance of high-alloyed metallic materials for transport tanks of dangerous goods and water-polluting substances. EUROCORR 2004 – The European Corrosion Congress, Nizza 2004
[12] Bäßler, R.; Weltschev, M., Werner, H.; Alves, H.; Behrens, R.: Beständigkeit von hochlegierten Werkstoffen beim Einsatz als Tankwandungs­werkstoffe zum Transport von Gefahrgut und wasserverunreinigenden Stoffen. DGO Jahrestagung, Sept. 2004, Dresden
[13] Weltschev, M.; Bäßler, R.: Bewertung der Beständigkeit von hochlegierten Sonderedelstählen und Nickellegierungen für den Transport von Gefahrgütern. Korrosionsschutzseminar: Hochlegierte Nichtrostende Stähle und Nickellegierungen in der Prozesstechnik, 6.-7. Oktober 2004, Dresden
[14] Bäßler, R.; Weltschev, M.; Werner, H.; Alves, H.: More Corrosion Resistant High-Alloyed Metallic Tank Materials for Transport of Dangerous Goods and Water-Polluting Substances. Stainless Steel World, Oktober 2004, Houston USA
[15] Weltschev, M.; Bäßler, R.; Werner, H., Alves, H., Behrens, R.: Use of Corrosion Resistant High-Alloyed Metallic Materials for Transport Tanks of Dangerous Goods and Water-Polluting Substances. EUROCORR September 4-8, 2005, Lissabon, Portugal
[16] Weltschev, M.; Bäßler, R.; Werner, H., Alves, H., Behrens, R.: Use of Corrosion Resistant High-Alloyed Metallic Materials for Transport Tanks of Dangerous Goods. Stainless Steel World Conference, November 8-10, 2005, Maastricht, Niederlande
[17] Weltschev, M.; Bäßler, R.; Werner, H., Alves, H.; Behrens, R.: Corrosion-resistant high-alloyed metallic materials for the transport of corrosive dangerous goods in tanks. CORROSION 2006, paper No 06688, NACE International, San Diego, USA, 2006

4. The Positive-Liquid List of DIN 6601

The axiom of concern according to § 19g para.1 of the Water Resources Act (WHG) indicates that equipment intended for the manufacture, treatment, or use of water polluting substances in the industrial sector must be procured, installed, positioned, maintained, and operated in such a way so as to ensure that no water pollution or other undesirable alterations of the waters properties occurs. As a result the general protection measures entail appropriate design and inspection of storage containers, including the verification of the resistance of the materials used in storage containers, conduits, and catch basins during long term exposure to the storage medium.

One of the first Positive-Liquid lists relating to the resistance of commonly used metallic materials of receptacles/tanks was published by a division of the German Institute for Standardization (DIN) the Tank Installations Standards Committee (NA Tank) as DIN 6601 – Resistance of steel materials from receptacles/tanks against liquids. This was done in conjunction with division III.2 of BAM "Tanks for Dangerous Goods and Accidental Mechanics", and the German Institute for Structural Engineering (DIBt) in October 1991.

The first amendment including commonly employed lubricants and hydraulic oils was published with the DIN 6601 draft in July 1994.

As a result of the requirement of evaluations of new material-liquid combinations on the part of the industry a new edition of the DIN 6601will be issued by DIN.

The evaluation of corrosion resistance is based upon published corrosion data of laboratory analysis and operational experience from the industry. They are only valid for commonly employed pure liquids, and mixed liquid substances with a well defined composition. The corrosions resistance of waste and mixtures is determined through corrosions analysis.

A material-liquid combination is assessed as suitable when

the rate of surface corrosion is no higher than 0.1 mm/year

  • local corrosions events, such as pitting corrosion, stress corrosion, and crevice corrosion aren’t expected.
  • With specific material-liquid combinations the positive resistance evaluations are only applicable when specific liquid related and operational conditions are adhered to.

If a material-liquid combination is deemed unsuitable on the basis of enacted evaluation precepts it may still in individual cases be deemed suitable by expert opinion of a materials testing institute, due to for example the adherence to supplementary requirements.

The storage of liquids not included in the Positive-Liquid list in receptacles composed of metallic materials is considered suitable when the acceptability of the material-liquid combination;

  • through service experience of no less than five years can be proved. Where these references are acknowledged by an expert in the field;
  • is indicated by recorded laboratory investigations of a materials testing institute or the operator with reproducible results and
  • when references found in corrosion literature are in concurrence.

The addition of new substances to the Positive-Liquid list is subject to conformation of Division 3.2 of the Federal Institute for Materials Research and Testing (BAM), 12200 Berlin.