Corrosion can pose a major risk to steel wire ropes. Light surface corrosion isn’t an immediate problem, but if the corrosion continues, the consequences can be disastrous. It can affect the steel wire rope to such an extent that the wire rope no longer functions properly or even breaks. In this article, we’d like to tell you more.
What is corrosion?
Corrosion is the natural deterioration of a material by the environment, such as oxygen, (salt) water or other chemicals. The use of different types of materials can also cause corrosion. This is called stress corrosion.
Degrees of rust
Check regularly if the steel wire rope has corroded. Rust has different degrees:
- Surface or fly rust. The wire surface isn’t affected. There is a slight cast of rust. Remove this and relubricate the wire rope with a suitable oil.
- Wire surface slightly corroded. No noticeable reduction in the wire diameter. Try to remove the corrosion. Is this possible? Then relubricate. Not possible? Then consult a specialist.
- Wire surface is corroded. Noticeable reduction of wire diameter. Slight gap between the outer wires. Consult a specialist.
- Wire surface strongly corroded. Clear reduction in wire diameter. Significant gap between outer wires. Consult a specialist.
- Pitting corrosion. Wire surface strongly corroded. Significant reduction in wire diameter. Gap between the outer threads is more than half the original diameter.
Do not relubricate a severely corroded steel wire rope
Note: do not relubricate a severely corroded wire rope. The corrosion under the lubricant will simply continue and will no longer be visible. If possible, have the wire ropes that are heavily corroded on the inside checked by a specialist.
Does the steel wire rope get thicker?
It’s also possible that a steel wire rope becomes thicker as a result of corrosion. Corrosion expands on the inside of the steel wire rope, resulting in a thicker rope. For this reason, if possible, a steel wire rope should be checked on the inside.
Stress corrosion can occur where two different types of steel are used and come into contact with each other. The steel types have different chemical compositions, resulting in one corroding the other. This often happens in combination with (salt) water. For example, a stainless steel wire rope may not be clamped with aluminum.
It’s therefore important to also check the wire rope fittings carefully when inspecting steel wire ropes. The rope fittings also present a risk for stress corrosion.
What can you do against corrosion?
Steel wire ropes are generally produced with a lubricant. This lubricant is twofold: it is a preservative and a lubricant. In many cases, it can take a long time for a steel wire rope to be used, so it is kept in stock. The lubricant then has a preserving function. The steel wire rope must not corrode. The moment the steel wire rope is installed, the lubricant has to start doing its job. It must lubricate in between the core and the strands as well as the wires themselves in the different strands. It’s recommended to lubricate the wire with an oil immediately after installation. The oil accelerates the lubricating effect.
We don’t lubricate with grease, but with a suitable oil that penetrates the core of the steel wire rope. Furthermore, it’s recommended to lubricate the steel wire rope regularly. The advice is twice a year for ropes that are used outside: once in spring and once in autumn. Please note: it’s important that you apply a thin layer of lubricant. Using too much is just as bad as no lubrication at all.
By regularly lubricating the steel wire rope with an oil, you slow down corrosion formation or prevent it as much as possible. Note: is the steel wire rope already corroded? Then lubrication is pointless and not recommended. The corrosion will simply continue from the inside, with all the associated consequences.
Get timely and in-depth advice on inspection for corrosion. When is corrosion a danger? Have your steel wire ropes inspected by Mennens. We belong to the ‘The Association of Recognised Inspection Companies for Lifting Equipment’ (EKH): all our inspectors have extensive experience and inspect according to the latest standards.