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September 22, 2022
Get a Better Understanding of ASTM A780 and Why We Exceed the Minimum Requirements
Written by: Sam Steele
ZRC is known across the globe for our cold galvanizing compound. It's a product we're truly proud of. One reason for this is that we not only meet the standards of ASTM A780 - we exceed them. Let's dig deeper into why we do so, and why this matters so much in the quality of your future project.
Who is ASTM?
The American Society for Testing and Materials, or ASTM, has a motto of "helping our world work better." This organization makes standards for just about everything you can think of, from the density of plastic to the thickness of string to, yes, the amount of zinc in cold galvanizing compounds. In fact, they have over 12,000 standards that inventors, engineers, architects, and construction crews must adhere to.
What is ASTM A780?
ASTM A780, in particular, relates to the products deemed acceptable in the repair of hot dipped galvanization. It sets the industry standard for whether or no paint is "good enough" to repair metal structures on the verge of corroding. The paint can provide a heavy-duty coating for large-scale structures such as bridges, infrastructure, and green power projects like solar and wind towers.
It does more than that, though. It also provides engineers and architects with an easy, quick way to write their spec sheets. Thanks to this standard, one can simply jot down "Must comply with ASTM A780" rather than writing out a long string of science, numbers, and data.
The person creating the spec sheet could reference a list of standards in the document; ASTM A780 is one of many, saving an enormous amount of time in the pre-construction phase of a project.
ASTM A780 states that zinc-rich paint must have zinc dust in the range of 65-69% or above 92% in the dried film in order to be effective against rust. These two ranges are said to be equally effective for repairing damaged galvanized coatings, but we only use 92% and above.
Why Is There a Gap in the Amount of Zinc Dust in the Paints Listed in ASTM A780?
You may wonder why two very different ranges are listed in ASTM A870 and how the two could possibly be considered equal. To be honest, they are not.
One study showed that galvanic action occurs in these ranges. The theory is that the galvanic action needed to combat rust doesn't occur in between.
Over the years of the ASTM, the standards have been weakened and softened by people who lobby to make it meet their products, rather than improve their products to meet the standard. ASTM A780 has been watered down to allow for cheap products to enter the market, but we are fighting this battle and will not lower our standards.
Why Do We Stick To 92% And Above?
We have been manufacturing zinc coating for over 70 years; we're technology pioneers. As the creators of cold galvanizing corrosion protection technology, we have maintained our position as a worldwide industry leader for years. Seven decades and four generations ago, our zinc-rich paint had at least 92% zinc and it still does today.
ZRC Worldwide has acquired industry-leading technical knowledge and expertise over decades that we are committed to sharing with our customers. With 95% zinc by weight in dried film, ZRC® Cold Galvanizing Compound exceeds ASTM A780 and SSPC Paint-20 standards. This is why we are proud to say we provide unmatched, lasting solutions.
We are a high-performance product. Plain and simple — keeping our paint at 92% zinc and above means it's more effective. More zinc means it works a lot better. Zinc, being less noble than steel, forms hydroxycarbonate salt when it corrodes that bonds with the existing zinc in the film coating while upholding galvanic protection. The zinc sacrifices itself to the underlying metal. While the zinc corrodes, the surface it's protecting does not. This creates an advanced, self-healing film that ensures the metal surface beneath the coating stays protected.
What Are the Risks of Using a Similar Product That Falls Within the 65-69% That Technically Still Meets ASTM A780?
Zinc applied as a protective top-coat is a lot easier, and more financially beneficial, to replace than the metal beneath it. The last thing you want is to undergo another repair project before you should need to do so. If you use a cheap product, you'll find yourself doing more and more repairs. A zinc-rich compound has a significantly longer lifespan than that of unprotected, oxidized metal.
A paint with less zinc, meaning a product that is 65% zinc rather than 92% is going to deteriorate a lot faster. When there's less zinc, it's not going to last as long and the rust will eat away at the metal instead of the zinc. Many of our competitors have a zinc content of 70% or lower, meaning their zinc-rich paint isn't really that rich at all.
"Good enough" is not good enough for you, and it's not good enough for us either. Less zinc means the metal will corrode faster. It also means that you'll need to paint again sooner.
Cheaper products may technically meet the standards, but a cheaper product will go away faster. Then, you're redoing it sooner. This is because zinc is the most expensive part of the coating. Your reputation is on the line with each project your team undergoes. As well, you should think long-term about expenses, not just ways to save money in the short term.
If we had our way, ASTM A780 would still have 92% zinc requirement. There are many products that service the varying needs of the corrosion prevention industry. Imitation is flattering, but the proof is in the paint. Don't just say use ASTM A780 in your spec sheet, specifically state you want ZRC. Use ZRC Worldwide by name!