Why the Surface Treatment Choice Matters
Selecting the correct surface treatment for rail spikes involves considering corrosion resistance, cost and the application environment. The right treatment protects the spike against moisture, salt and chemical attack, keeps the thread and holding surfaces in good condition, and determines how long the fastening remains reliable before maintenance is needed.
Treatment Options by Cost and Corrosion Resistance
The table below compares the common surface treatments for rail spikes.
| Treatment | Relative Cost | Corrosion Resistance | Typical Use |
|---|---|---|---|
| Plain oiled | Lowest | Temporary | Short-term storage and dry service |
| Blackening with oiling | Low | Moderate | Industrial fasteners indoors |
| Electro galvanizing | Medium | Good | General outdoor track fastening |
| Hot dip galvanizing | High | Excellent | Long-term outdoor and coastal service |
| Dacromet coating | Highest | Excellent | Corrosive environments without hydrogen embrittlement |
Plain oiled finish is the cheapest option and provides only temporary protection against corrosion. Blackening with oiling is a popular low-cost method often used for industrial fasteners. Electro galvanizing is a cost-effective plating method with good corrosion resistance. Hot dip galvanizing provides excellent corrosion resistance for long-term use but is more expensive than electro galvanizing. Dacromet coating offers excellent corrosion resistance and high-temperature stability, without introducing hydrogen embrittlement, but it is costlier.
Consider the Project Cost and Environmental Conditions
The budget of the project determines the most suitable treatment. Plain oiling is the cheapest, while specialized coatings are the most expensive. For projects where the spike will be stored briefly and installed in a dry environment, low-cost treatments can be sufficient, but for permanent track installations the protection level should match the expected service life of the line.
Consider the environment where the spikes will be used. Harsh or corrosive conditions, such as coastal lines, tunnels, chemical plants and regions with de-icing salt, may require more robust protection like hot dip galvanizing or Dacromet coating. In clean inland areas with low rainfall, electro galvanizing or blackening may be adequate.
Consider the Service Life
For long-term applications, treatments that offer superior corrosion protection, such as hot dip galvanizing, are recommended over basic oiling. The zinc layer of hot dip galvanizing corrodes preferentially and protects the steel for many years, while a plain oiled surface needs regular re-oiling and gives little protection once the oil film is lost.
Consider the Specific Application
Specialized requirements may make other treatments more appropriate. Where hydrogen embrittlement is a risk, for example with high-strength heat treated spikes, Dacromet coating avoids the hydrogen charging associated with some plating processes. Where high temperatures are expected, coatings with good thermal stability should be selected, and where dimensional tolerance is critical, thin coatings such as electro galvanizing preserve the thread profile better than thick hot dip layers.
Frequently Asked Questions
What is the cheapest surface treatment for rail spikes? Plain oiled finish is the cheapest and provides only temporary protection.
Which treatment gives the best long-term corrosion resistance? Hot dip galvanizing and Dacromet coating provide excellent long-term corrosion resistance.
What is the difference between electro galvanizing and hot dip galvanizing? Electro galvanizing gives a thinner, smoother coating at lower cost, while hot dip galvanizing gives a thicker, more durable zinc layer.
Why choose Dacromet coating? Dacromet provides excellent corrosion resistance and high-temperature stability without hydrogen embrittlement.
Which treatment suits coastal lines? Hot dip galvanizing or Dacromet coating is recommended for coastal lines with high salt exposure.
Does treatment affect the thread profile? Yes, thick coatings such as hot dip galvanizing can fill the thread, so thin coatings are preferred where tight tolerances matter.
