Of the environmental conditions in which engineering products daily have to operate, none poses a greater or wider problem than sea water and the associated saline atmosphere, which frequently exists for many miles inland.
The life expectancy of equipment is often drastically reduced and 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 is a variety if differing but equally costly ways: -
Carbon Steel
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 even stress corrosion.
Stainless Steels
Are highly prone to chloride pitting a particularly damaging form of crevice corrosion producing small holes in material having an otherwise sound appearance.
Tungum Alloy
TUNGUM ALLOY was developed specifically to counter the problems of sea water and in practice has already done so for over 40 years.
Whether totally immersed, or in the highly active ‘splash’ zone Tungum Alloy affords exceptional resistance to the effects of marine environment. Unaffected by either stress or crevice corrosion, Tungum Alloy is protected by a speedily self generated oxide coating which, once formed, prevents further attack. If this oxide coating is damaged it does of course quickly repair itself.
Tungum alloy tube remains unscathed despite more than 10 years marine exposure on a semi-submersible support vessel. The stainless steel section, from a southern North Sea gas platform, shows both crevice corrosion and chloride pitting after barely five years in the same environment, in lines under pipe clamps.
The special corrosion resisting characteristics of Tungum Alloy tubing, carefully developed for use in the hydraulics systems of marine aircraft remains just as valid in todays polluted sea waters.
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 protective coating 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.
Galvanic Series Of Engineering Materials
The table opposite shows the relative position of Tungum Alloy to other well known materials when placed in galvanic series.
In general significant galvanic corrosion does not take place when copper is coupled to its alloys or when different copper alloys are in contact with each other. The amount of galvanic corrosions on a less noble metal will depend on the relative areas of the two metals in contact and the potential or voltage existing between them in a given environment.
For example a large mass of copper, or its alloy should not be coupled to a small mass of reactive material such as iron, zinc or aluminium. On the other hand the coupling of a copper, or its alloy having a small area relative to the area of the more reactive metal will often prove to be satisfactory.
Generally a good electrical contact in a metal to metal joint will be greatly reduce the possibility of galvanic corrosion.
- Tungum Alloy Tube
- Marine Corrosion Resistance of Tungum Alloy
- Physical Properties of Tungum Alloy
- Comparative and Elevated Temperature Performance
- Fatigue and Low Temperature Characteristics
- General Corrosion Resistance
- Designing with Tungum Alloy
- Tungum Alloy Tubing Metric Range
- Tungum Alloy Tubing Imperial Range
- Specifications and Approvals
- Fabricating Systems in Tungum Alloy
- Information Request Form
| Substance | Potential mV |
|---|---|
| Magnesium | 1730 |
| Ng-4% Al Solid Solution | 1680 |
| Galvanised Iron | 1140 |
| Cd-Zn Solder (71/29) | 1120 |
| Mg5Al8 | 1070 |
| Zinc | 1050 |
| MgZn22 | 1040 |
| Al-4% Zn Solid Solution | 1020 |
| Al-Zn-Cu Alloy 3L5 | 990 |
| Al-1% Zn Solid Solution | 960 |
| Al-4% Mg Solid Solution | 870 |
| Cd-Plated Steel | 850 |
| MnAl6 | 850 |
| Aluminium (99.95%) | 850 |
| Al-Zn-Mg-Cu-Ni Alloy RR77 | 840 |
| Al-Zn-Mg-Cu-Cr Alloy 75S | 840 |
| Aluminium (90.0%) | 830 |
| Al-11.9% Si Alloy N2 | 830 |
| Al- 1 1/4% Mn Alloy N3 | 830 |
| Al-1% Mg Si Solid Solution | 830 |
| Al-Si-Cu-Ni-Fe Alloy DTD.133B | 810 |
| Clad H14 Alloy | 810 |
| Mild steel 353 | 780 |
| Grey Cast Iron | 780 |
| Tinplate | 740 |
| Al-7% Mg Alloy | 690 |
| Al-4% Cu Solid Solution | 690 |
| Al-Cu-Mg-Mn Alloy H14 | 680 |
| Iron (pure) | 580 |
| FeAl3 | 560 |
| Tinman’s Solder | 560 |
| Lead | 550 |
| Cu Al2 | 530 |
| Tin | 500 |
| Brass (60/40) | 330 |
| Aluminium Brass | 290 |
| Silicon | 260 |
| Cupro-Nickel (70/30) | 260 |
| TUNGUM ALLOY | 230 |
| Copper | 220 |
| Stainless Steels (316 = 195mV) | 130-430 |
| Monel | 170 |
| Nickel | 140 |
| Silver | 80 |
| Graphite | |
| Gold | |
| Platinum |
Company Registration No. 282202