A study released this week has revealed the limitations of galvanized steel and its inability to withstand exposure to the most common corrosive agent, sodium chloride.
The study, which was performed by Daubert Chemical in accordance with the American Section of the International Association for Testing and Materials (ASTM) B117 standards, compared galvanized steel I-beams to I-beams coated with Daubert’s Nox-Rust 1210HP wax-based coating.
The company says it performed the experiment in response to its OEM customers’ inquiries regarding the viability of galvanized components in trailer chassis construction.
“Questions about the use of galvanized steel chassis components have arisen among truck and trailer OEMs in recent years,” says Mike Duncan, Ph.D., vice president technology for Daubert Chemical. “As we discussed the topic with our customers, we realized that nobody had done a definitive study on the subject, and that’s when we decided to undertake formalized testing.”
Also known as salt fog testing, the ASTM B117 is a standardized method used to assess the corrosion resistance of various surface coatings and is often used in side-by-side comparisons that demonstrate the relative effectiveness of different coatings. Salt spray testing is an accelerated corrosion test that approximates the long-term protective efficacy of a coating and is equally effective at predicting its failure rate, Daubert says.
The test results showed that after 1,000 hours of exposure to the saline spray, the galvanized steel I-beam underperformed in comparison to the I-beam coated with Nox-Rust 1210HP wax-based coating. The continuous salt spray exposure caused the galvanized sample to begin visibly shedding its protective zinc coating in the form of zinc oxide, also known as white rust, the company says.
Additionally, the zinc coating used in the galvanizing process is known as a sacrificial anode because it corrodes first, in preference to the metal substrate it is designed to protect. In contrast, Daubert says wax-based coatings are hydrophobic and repel water molecules, preventing the oxidation that can be caused by moisture contacting the metal beneath its protective layer.
