Tungum has excellent anti-corrosion properties

Tubing: Corrosion Resistance Offshore
The environmental conditions in which engineering products have to operate are by their nature fairly arduous.

None poses greater or wider problems than sea water and the associated saline atmosphere.

The life expectancy of equipment is often drastically reduced. In areas where corrosion has already taken place, predicting failure as a basis for preventative maintenance is difficult if not impossible.

At its most aggressive, in the presence of oxygen, sea water attacks most ‘standard’ materials in a variety of differing but equally costly ways: –

Carbon Steels
Prove almost impossible to protect and corrode away almost immediately.

Common Copper Alloys
Often suffer a shortened life, either as a result of dezincification or stress corrosion.

Stainless Steels – 304, 316
Are highly prone to chloride pitting a particularly damaging form of crevice corrosion producing small holes in material having an otherwise sound appearance.

Super Duplex and Austenitic Stainless Steels – 904L, Monel, 6Mo-Alloy 400, and 2507
Although these materials are far more corrosion resistant, than St.Steels, they are not corrosion proof and do suffer pitting and crevice corrosion after time.

Tungum alloy tubing C69100
Tungum Tubing has been developed to counter the problems of sea water corrosion and in practice has already done so for over 40 years.

Whether totally immersed, or in the highly active ‘splash’ zone, Tungum alloy tubing gives exceptional resistance to the effects of a marine environment.

Unaffected by either pitting or crevice corrosion, Tungum alloy tubing is protected by its oxide coating.

This oxide coating quickly repairs itself if damaged.

Natural Protection Mechanism

Tungum tubing remains unscathed despite more than 10 years marine exposure on a semi-submersible support vessel. The Stainless Steel section, from a southern North Sea platform, shows both crevice corrosion and chloride pitting after barely 5 years in the same environment.

Protective Oxide CoatingThe special corrosion resisting characteristics of Tungum tubing, carefully developed for use in the hydraulics systems of marine aircraft remains just as valid in today’s polluted sea waters.

Weight Loss Graph

The development of the oxide coating is illustrated by the graph.This shows time plotted against a minute weight loss during its formation.After 1000 hours the weight has virtually stabilised indicating that the protectivecoating is already almost complete.A fact confirmed in the laboratory by the most rigorous tests and backed by experience of countless practical and demanding applications. Many of these more than 50 years standing.Corrosion AllowanceAs a result of the excellent corrosion resistance characteristics of Tungum and integrity management feedback received, a corrosion allowance not generally required for Tungum tubing when used in suitable applications

Corrosion Testing

Tungum corrosion testing results can be found in various articles including:NACE TestingNACE Paper No. 10305 entitled ‘316 Stainless Steel Instrument Tubing in Marine Applications – Localized Corrosion Problems and Solutions.’ This paper compares various metallic materials in addition to Tungum Alloy (UNS C69100) including 316L, 317LMN (UNS S31726), Alloy 825 (UNS N08825), 6Mo (UNS S31254), Alloy 625 (UNS N06625) and underpins the historical evidence of successful performance in these demanding safety critical applications.Materials were laboratory tested in a cyclic salt fog chamber to ASTMD5894 at temperatures ranging from 25 to 45 degrees C and also fieldtested by exposure to a marine environment for a one year duration onboard two offshore platforms; one located in the Gulf of Mexico and theother in Trinidad.In the laboratory tests Tungum Alloy (UNS C69100) was the material that resulted in the best localized corrosion resistance judging by two of the three visual inspection indicators 

  • pit depth in the body of the tubing
  • crevice corrosion depth.

Conclusions were that Tungum Alloy (UNS C69100) is a material that can be safely used in a marine atmosphere keeping in mind its pressure and internal corrosion limitations.The results of the test were published in NACE Paper No. 10305 and presented at the NACE CORROSION 2010 Conference & Expo. A copy of the paper can be obtained direct from:NACE International website

Other Corrosion Tests – PREN, G48 and CPT

Various corrosion related tests and calculations including PREN, G48 and CPT can be applied to stainless steel and related nickel and chromium based alloys, but:None of these tests are appropriate for Tungum as it is a copper based alloy, as explained below.

PREN (Pitting Resistance Equivalent Number). NACE and NORSOK typically require a PREN of 40 minimum for oil and gas applications. Normally calculated using the formula: PREN = wt%Cr 3.3wt%Mo + 16wt%N. This formula, however, cannot be applied to Tungum because it is a unique copper based alloy and does not contain any Molybdenum or Chromium.

ASTM G48 Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys. By definition this standard does not apply to copper based alloys.

CPT (Critical Pitting Temperature) for Stainless Steels and Related Alloys. This can be determined either by ASTM G48 method C or E. Alternatively, using electrochemical test methods to ASTM G150 Standard Test Method for Electrochemical Critical Pitting Temperature Testing of Stainless Steels. Again, by definition these standards do not apply to copper based alloys.

General Corrosion Resistance By Substance

Excellent resistance – minimal attacks take place – for the following substances:

Substance Maximum ConcentrationMaximum Temp °C
Acetic Anhydride0-10020
Carbon Tetrachloride-Boiling
Cotton Seed OilAll20
Cryesylic AcidAll20
Formic Acid0-5020
Lactic AcidAll20
Halic AcidAll20
Magnesium Chloride0-1050
Methylene Chloride-Boiling
Oleic AcidAll20
Oxalic Acid25grms./100c.c20
Potassium BromideS.S.20
Potassium NitrateAll20
Sodium ChlorideS.S.20
Sodium HydroxideS.S.20
Sodium Hypochlorite1% Av.Cl.50
Sodium MetabisulphateS.S.20
Sodium SulphateS.S.20
Sodium Sulphite0-1050
Stearic AcidAll20
Tannic AcidAll20
Tartaric AcidAll20
Zinc Chloride-20
Zinc ChlorideS.S.20

Good resistance under the conditions of test were achieved for the following substances:

SubstanceMaximum ConcentrationMaximum Temp °C
Aluminium Sulphate0-4020
Calcium Bi-SulphateAll70
Citric AcidAll20
Hydrochloric Acid0-1020
Hydrogen Sulphide(H2S)2500 p.p.m.-
Phosphoric Acid0-10100
Picric AcidAll20
Salicylic AcidS.S.20
Sodium Bicarbonate--
Sodium HypochlorideS.S.70
Sulpher Dioxide--

Note: Tungum Tubing should not be used in the presence of Acetylene, Ammonia or Mercury.

These ratings are the result of laboratory tests conducted in-house under the controlled conditions noted. They are published for guidance only. Where any doubt exists, samples of Tungum are freely available for field trials to replicate the precise operating conditions.

Tungum Tubing has a high level of general corrosion resistance, allowing it to be specified for use in systems containing, or operating in the presence of a variety of substances and solutions.