Fasteners for Sulfuric Acid (H2SO4)

Sulfuric Acid (H2SO4) is one of the most widely used and industrially important acids in modern society, being an essential component in the production of polymers, fuels, pharmaceuticals, electronics, and mining. While sulfuric acid is commonly used, enabling fasteners to survive in this environment is not always an easy task. To help you tackle this feat, let’s discuss some material options and factors to consider in H2SO4 environments.

A common question we get at Special Fasteners China. & Fastener is: “What is the best fastener material in H2SO4 environments?” To answer this questions correctly there are a few aspects that must be considered.


1. What is the temperature of your application?
H2SO4 behaves as you might expect with respect to temperature but it is a fairly sensitive variable. To put it simply, as temperature increases so does the corrosion rate but be cautious – the corrosion rate can increase rapidly with only small changes in temperature. So, temperature is usually more of a concern from a corrosion point of view than the usable temperature limits of the material since most H2SO4 environments are not above 200°C/400°F.

2. What is the concentration of H2SO4 ?
The corrosiveness of H2SO4 is highly dependent on the concentration. Logically, H2SO4 is less corrosive at a lower concentration and more corrosive at higher concentrations. This remains true when dealing with concentrations of 99% or less. For example, as you would expect a concentration of 97% H2SO4 is far more corrosive than that of 6%.Corrosion Resistant Fasteners

Yet, there is an exception to this rule when dealing with concentrations of 99% or greater. In such high concentrations, H2SO4 is not very corrosive at all. In fact, H2SO4 at these levels can be handled simply with carbon steel. So counter intuitively, a concentration of 99% is far less corrosive than a concentration of 98%.

However if your concentration is changing due to dilution this can be a bit tricky as well. Typically as you diluteacids they become less corrosive however in the case of sulfuricacid, as it is diluted it gives off heat (exothermic). Although dilution brings the concentration down, the temperature will increase (an increase in temperature heightens the corrosion rate: See Point 1) and therefore the solution could become more corrosive until the heat is removed.

3. What are your performance requirements and corrosion resistance expectations?

The ease of which a fastener may be replaced might dictate which material is best. For example, are the fasteners for a critical piece of process equipment that cannot go down without serious economic implications? If so we may recommend a fastener that exhibits no corrosion rate at all. Or is the fastener for a laboratory experiment that may be used once or twice? In this case, we may suggest a fastener that has a slow corrosion rate but is far less expensive than a material with no corrosion rate at all. Understanding such factors allows you to better select the appropriate material in the most economical way for your job. The following chart gives a general ranking of the corrosion resistance of some of the more corrosion resistant materials we offer.
4. What are the mechanical requirements of the fastener?
Corrosion Resistant Ceramic Fasteners As for all fastener applications, it’s obviously important to consider the load and mechanical requirements of the application. Materials such as polymers, ceramics and metals could be used in H2SO4, so there is a range of material options that may be considered.

 

While the complete chemistry of the process stream, potential contamination, operating conditions,and mechanical requirements must be considered, these charts list some excellent options for H2SO4 environments.Corrosion Resistant Polymer Fasteners For more information about which material might be best for your H2SO4 environment
contact one of our materials expertsor learn more at www.specialfastenersbolt.com.Sulfuric Acid Iso Corrosion Curve by Metal
H2SO4 iso-corrosion curve comparing various high performance metals corrosion resistance. Each line represents a corrosion rate of 5 mils per year. The further the operating point is below the curve the better.
This entry was posted in Blog and tagged , , , , , , , , , , . Bookmark the permalink.

Leave a Reply

Questions?

Our material experts are ready to help guide you through your specific application.

Contact an Expert