Bearing rusting
Why has the bearing rusted again? This is a frustrating issue for many customers. In fact, rust isn’t something to fear—once you identify the root cause, it’s easy to resolve!
Why has the bearing rusted again? This is a frustrating issue for many customers. In fact, rust isn’t something to fear—once you identify the root cause, the problem is easily resolved!
Next, Little Scissors will take you deep into the issue—what’s the solution when bearings keep rusting?
Rusting is a form of corrosion, which in turn is classified into two types: chemical corrosion (contact corrosion) and electrochemical corrosion (corrosion involving an electric current).
The rusting of iron exposed to air is, in fact, a galvanic cell reaction.
The reaction equation here is:
2Fe + O2 + 2H2O ==== 2Fe(OH)2
4Fe(OH)2 + O2 + 2H2O ==== 4Fe(OH)3
2Fe(OH)3====Fe2O3·xH2O＋(3-x)H2O
Fe2O3·xH2O is rust.
It’s okay if you don’t get it—simply put, there’s rust on a perfectly good bearing. ~~
Locations of corrosion: Corrosion can occur on all surfaces of the component. Depending on its severity, it may manifest as corrosion spots or pitting; these spots and pits are typically scattered or densely distributed, with irregular shapes and variable depths, and exhibit colors ranging from light gray to reddish-brown, grayish-brown, or black.
For rolling bearings, the main causes of corrosion are:
1. The bearing interior or the lubricant contains corrosive substances such as water, alkali, and acid.
2. The heat generated during bearing operation is not dissipated in a timely manner, leading to moisture formation upon cooling.
3. Failure of the sealing device
4. The bearing is used in a high-humidity environment.
5. Improper cleaning, assembly, and storage
Most of the causes are related to material selection and operating conditions; eliminating corrosion is actually quite challenging and cannot be achieved simply by sanding with abrasive paper. The underlying mechanisms can be broadly categorized into the following two principles:
1. However, it can slow down the onset of corrosion and prevent the bearing from coming into contact with corrosive substances.
2. Corrosion resistance can be enhanced through alloying, surface modification, and other methods, enabling the formation of a stable, dense passivation film on the metal surface that adheres strongly to the substrate.
The most common approach is to employ the first principle:
After completion of critical processes, the bearing plant employs multiple washings and repeated rust‑proofing to remove contaminants and applies anti‑rust oil to isolate oxidizing and corrosive substances.
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