Not all contamination is dust. Gaseous contamination corrodes equipment slowly from the inside, a problem that only becomes visible once failures appear. Here is what is going on.
The culprits
Sulfur-bearing gases such as hydrogen sulfide (H₂S) and sulfur dioxide (SO₂) are the main drivers. They enter with outside air from industry, traffic or nearby processes and attack exposed metal.
Creep corrosion
On circuit boards, corrosion forms on copper and silver and then “creeps” across the surface, a process called creep corrosion. Eventually it bridges contacts and causes failures, with no obvious physical damage.
How it is measured
Air corrosivity is measured with copper and silver reactivity coupons, expressed in Ångströms of buildup per month. ASHRAE recommends G1 level: below roughly 300 Å/month for copper and 200 Å/month for silver.
The role of dust
Dust worsens gaseous corrosion: hygroscopic particles hold moisture and concentrate corrosive species right on components. A clean environment is therefore the first line of defence, alongside gas-phase filtration where needed.
Key takeaways
- Sulfur gases attack copper and silver.
- Creep corrosion bridges contacts and disrupts.
- Measured with reactivity coupons (G1 target).
- Dust accelerates corrosion; staying clean helps.