In one of the first presentations at the 2024 AMPP Annual Conference + Expo, GPI’s Chris Farschon, PCS, and Charles Brown, PCS, offered an overview of protection strategies against steel corrosion during Sunday’s Coatings 101 Workshop.

"Steel corrosion is the irreversible deterioration and destruction of the steel material and its vital properties due to the electrochemical or chemical reaction of its surface to environmental factors such as acids, moisture, and oxygen," the presenters noted.

"Steel corrosion involves electrolysis in which the metallic surface releases electrons into an electrolyte, such as a layer of moisture in the presence of oxygen. This electrochemical reaction occurs due to the tendency for metals to return to their natural state. Iron in the steel in the environment of moist air will tend to go back to its original state of iron oxide as rust. Steel can be corroded by the chemical reaction of certain chemicals like sulfuric acid."

In short, as Brown said, it's "the destruction of steel that can be detected when rust forms."

According to the presenters, four conditions are necessary for corrosion. These include:

Anode: The electrode where galvanic reaction(s) generate electrons. Negative ions are discharged and positive ions are formed. Corrosion occurs at the anode.

Cathode: The electrode that receives electrons. Positive ions are discharged, negative ions are formed. The cathode is protected from corrosion.

Electrolyte: The conductor through which current is carried. Electrolytes include aqueous solutions or other liquids.

Return Current Path: The metallic pathway connecting the anode to the cathode. It is often the underlying metal substrate.

Two primary means to prevent this steel corrosion involve protective coatings (barrier, inhibitive, and sacrificial) and cathodic protection (impressed current, sacrificial protection). For purposes of this presentation, the emphasis was on coatings.

Whatever the chosen coating technology, GPI sees six steps as necessary to ensure a quality corrosion protection system. These incorporate good design, good paint, good specifications, good contractors or applicators, good inspection, and good maintenance.

The remainder of the presentation involved in-depth discussions regarding strategies to achieve those six steps. Further details are available by contacting Brown at cbrown@gpinet.com.

In conclusion, Brown and Farschon noted that a successful coating project requires a complete and thorough understanding of corrosion; coatings and their chemistry; industry standards; specifications; surface preparation and application techniques; inspection strategies, including hold points, equipment, and communication; and maintenance needs.