Thickness isn't the only thing that matters in galvanized sheet — the zinc coating weight determines how well it resists rust. We look at how this hidden spec affects price.
Two galvanized sheets with the same thickness are in front of you, and one is noticeably cheaper than the other. The customer asks why. The answer is usually found in something that cannot be seen at a glance: zinc coating weight. This hidden specification determines both the price and how many years the sheet will last against rust.
What Is Coating Weight and Why Is It More Important Than Thickness
Galvanized sheet is sheet steel whose surface is covered with a layer of zinc (Zn) to protect it against rust. The amount of this coating is measured by coating weight, meaning grams of zinc per square meter of surface. Two sheets may have exactly the same base steel thickness, but if one has a lower coating weight, that sheet will rust sooner. That is why, with galvanized sheet, checking only the thickness is only half the story.
It is this immersion in the molten zinc bath that determines the actual thickness of the zinc layer and, consequently, the sheet’s service life against rust.
How Coating Weight Affects Price and Selection
A sheet with a higher coating weight has consumed more zinc, so it is more expensive and lasts longer in humid environments or outdoors. A sheet with a lower coating weight is cheaper and sufficient for indoor, low-humidity applications. Your role is to understand where the customer intends to use the sheet and recommend the appropriate coating weight, rather than simply selling the cheapest option.
| Specification | Its Effect | Sales Note |
|---|---|---|
| High coating weight | Greater resistance to rust, longer service life | Suitable for outdoor and humid environments; more expensive |
| Low coating weight | Lower resistance, lower price | Suitable for indoor, low-humidity applications |
| Base steel thickness | Mechanical strength of the sheet | Separate from coating weight; both must be checked separately |
A Warning to Buyers and Sellers
The most common misunderstanding in the galvanized market is that buyers assume two sheets with the same thickness are equal and only choose the cheaper one. If, as a seller, you do not clearly explain this difference, or if you purchase without paying attention to coating weight, you may sell a sheet that rusts sooner than the customer expects, putting your reputation at risk. Well-known brands such as Haft Almas, Taraz, and Kashan usually include the coating weight in their specifications; use it as the basis for comparison.
Frequently Asked Questions
گرماژ در ورق گالوانیزه یعنی چه؟
گرماژ یعنی مقدار پوشش روی (Zn) روی سطح ورق، که برحسب گرم بر مترمربع بیان می‌شود. هرچه گرماژ بیشتر باشد، لایهٔ محافظ ضخیم‌تر و مقاومت ورق در برابر زنگ بیشتر است.
چرا فقط به ضخامت ورق گالوانیزه نگاه نکنیم؟
چون دو ورق با ضخامت یکسان می‌توانند گرماژ پوشش روی کاملاً متفاوتی داشته باشند. ورقی با گرماژ کمتر ارزان‌تر است اما زودتر زنگ می‌زند؛ اگر فقط ضخامت را چک کنید، این تفاوت مهم را نمی‌بینید.
تولیدکنندگان اصلی ورق گالوانیزه در ایران کدام‌اند؟
هفت‌الماس (از بزرگ‌ترین‌ها)، تاراز، کاشان و شهرکرد از نام‌های شناخته‌شدهٔ بازار هستند و ورق گالوانیزه را در ضخامت‌های حدود ۰.۱۸ تا ۲.۵ میلی‌متر تولید می‌کنند.
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