Question 1

Learn how to test the actual coating weight (zinc or aluminum-zinc) of prepainted steel coil substrates using a simple gravimetric method. This guide covers sample preparation, acid stripping, weighing, and calculation for GI and GL base materials.

Accepted Answer

How to Accurately Test the Coating Weight of Prepainted Steel Coil Substrate – A Step-by-Step Guide 📅 Published: August 25, 2026 | By Fanda Steel 📌 Summary: For buyers and quality control professionals, verifying the actual coating weight of prepainted steel coil substrates is essential to ensure you receive the specification you paid for. This guide provides a practical, laboratory-based method to test zinc or aluminum-zinc coating weight on GI and GL base materials. Why Coating Weight Testing Matters Prepainted steel coils (PPGI/PPGL) are widely used in roofing, wall cladding, and industrial applications. The substrate — typically hot-dipped galvanized steel (GI) or Galvalume steel (GL) — provides the fundamental corrosion resistance that determines the product's service life. However, not all coils deliver the specified coating weight. Substitution with lower-grade materials (e.g., AZ30 instead of AZ150) is a common quality issue that only becomes apparent through testing. This guide outlines a simple, reliable gravimetric method to determine the actual coating weight of the substrate — a test that can be performed in a basic laboratory setting. Materials You Will Need Item Purpose Prepainted steel coil sample Test material Circular cutting die (80mm diameter) To cut uniform samples Analytical balance (0.001g accuracy) For precise weighing Concentrated sulfuric acid (H₂SO₄) To strip the paint coating Hydrochloric acid (HCl) To strip the zinc/Al-Zn coating Distilled water For rinsing Drying oven or hot air blower To dry samples Desiccator To cool samples before weighing Vernier calipers To measure sample thickness (optional) Step-by-Step Testing Procedure Phase 1: Sample Preparation Cut three circular samples from the prepainted coil using an 80mm diameter cutting die. Mark or label each sample for identification (e.g., Sample A, B, C). Measure the exact diameter of each sample to calculate the surface area. Area (m²) = π × (Diameter in meters / 2)² For an 80mm diameter sample: Area = 3.1416 × (0.080 / 2)² = 0.005027 m² Total area  = 0.005027 Phase 2: Paint Stripping (Remove the Organic Coating) Weigh each sample on the analytical balance and record the initial weight (W₁). Place the samples in a container filled with concentrated sulfuric acid (H₂SO₄). Allow to soak for several minutes — the acid will dissolve and remove the paint film completely. Observe until the coating is fully stripped. Remove the samples from the acid bath. Rinse thoroughly with distilled water to remove all acid residue. Wipe dry with a clean cloth, then dry completely using a drying oven or hot air blower. Cool the samples in a desiccator to room temperature. Weigh each sample again and record this weight (W₂). W₁ – W₂ represents the weight of the paint coating (if needed for separate analysis). The sample now consists of: steel substrate + zinc/Al-Zn coating. Phase 3: Coating Stripping (Remove the Zinc/Al-Zn Layer) Place the stripped samples (from Phase 2) into a container filled with hydrochloric acid (HCl). Allow to soak until the zinc or aluminum-zinc coating is completely dissolved. Continue until bubbling stops and the surface appears as bare steel. Remove the samples from the acid bath. Rinse thoroughly with distilled water. Wipe dry with a clean cloth, then dry completely using a drying oven or hot air blower. Cool the samples in a desiccator to room temperature. Weigh each sample one final time and record this weight (W₃). W₂ – W₃ represents the weight of the zinc/Al-Zn coating removed. Phase 4: Calculation Calculate the coating weight per square meter (g/m²) for each sample: Coating Weight (g/m²) = (W₂ – W₃) / Total Area (m²) Example Calculation: Parameter Value Sample diameter 80mm (0.080m) Total area  0.005027 m² W₂ (after paint removal) 16.9697g W₃ (after coating removal) 16.1720g Weight difference (W₂ – W₃) 0.7977g Coating Weight = 0.7977g / 0.005027 m² = 158.6 g/m²This result corresponds to AZ150 (150 g/m²) coating specification. What the Results Tell You Coating Weight Range Corresponding Specification Typical Application 20–40 g/m² AZ20 / Z20 Short-term interior 70–100 g/m² AZ70 / Z100 General exterior 100–130 g/m² AZ100 / Z120 Standard roofing 130–180 g/m² AZ150 / Z180 Coastal/premium 180–220 g/m² AZ200 / Z220 High-corrosion areas If your specified AZ150 coil tests at 80 g/m², you have received a lower-grade product than ordered — a common quality issue that this test can identify. Important Notes and Precautions ⚠️ Safety First: Concentrated sulfuric acid and hydrochloric acid are corrosive. Wear appropriate PPE (gloves, goggles, lab coat). Perform all acid handling in a fume hood or well-ventilated area. Neutralize acid waste properly before disposal. 📌 Accuracy Tips: Use an analytical balance with 0.001g precision for reliable results. Ensure samples are completely dry before each weighing — moisture will affect accuracy. Handle samples with tweezers to avoid contamination from fingerprints. Calculate the average of three samples for a representative result. 📋 Additional Considerations: This method measures the coating weight on both sides of the substrate (top and bottom). For prepainted coils, the paint layer is typically 15–25μm (PE) or 20–30μm (PVDF) — the paint weight can also be calculated from W₁ – W₂ if needed. For Galvalume (GL) substrates, the coating composition is 55% Al, 43.5% Zn, 1.5% Si — the same stripping method applies. Why This Test Matters for Your Business For buyers and quality assurance teams, this simple gravimetric test provides objective evidence of coating quality. It is: Quantifiable — Provides a specific, verifiable number in g/m² Reproducible — Can be repeated by any laboratory Defensible — Results can be documented and shared with suppliers At Fanda Steel, we conduct this test on every batch of prepainted steel coils before shipment. We believe in transparency and welcome third-party verification of our coating quality. When you specify AZ150, we deliver AZ150 — not a substitute. 📩 Contact Us for Coating Test Documentation or Technical Inquiries Email: sales@fandasteel.com | WhatsApp: +86 185 5336 6695

Question 2

Can I get a sample before placing an order ?

Accepted Answer

Can I get a sample before placing an order? Yes, we welcome sample orders. Fanda Steel provides samples for quality verification before you proceed with bulk orders. 📦 Sample Policy: Small samples (e.g., small pieces of coil, corrugated sheet, or tile) – Free of charge, but customer pays for shipping. Large samples (e.g., full guardrail beam, full tile) – Sample fee applies, but refundable upon formal order. Custom samples – According to your specifications and drawings, we can produce samples upon request (lead time and cost vary). ⏱️ Sample Lead Time: Small samples: 7–10 days Custom samples: 15–20 days 📩 How to request a sample? Please contact our sales team with your product requirements and delivery address. We will confirm the shipping cost and arrange the sample accordingly. 👉 Contact us now to request your sample

Question 3

we produce the highway guardrail as per the drawings

Accepted Answer

❓ What is the standard of the highway guardrail? Fanda Steel produces highway guardrail products in accordance with internationally recognized standards to ensure safety, quality, and compatibility with global infrastructure projects. We offer guardrail products manufactured to the following standards: AASHTO M180 – American standard for corrugated steel highway guardrails, widely used in the United States and regions following US specifications JT/T 281-2023 – China standard for highway guardrails, applicable to projects in China and countries adopting Chinese technical standards Customized per client drawings – We can also manufacture guardrail beams, posts, and accessories according to your specific design requirements and project specifications Available guardrail products include: Double-wave and triple-wave guardrail beams Round and square guardrail posts Spacer blocks and anti-blocking devices Bolts, nuts, and other connecting accessories End terminals and transition sections Standard material: Hot-dipped galvanized steel (Z275–Z600 coating) for corrosion resistance and long service life. For projects requiring specific standards or certifications, please contact our team to discuss your requirements. { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What is the standard of the highway guardrail?", "acceptedAnswer": { "@type": "Answer", "text": "Fanda Steel produces highway guardrail products according to AASHTO M180 (American standard), JT/T 281-2023 (China standard), or customized per client drawings. Products include double-wave and triple-wave guardrail beams, posts, spacer blocks, bolts, end terminals, and accessories, all made from hot-dipped galvanized steel (Z275-Z600 coating). Contact us for project-specific requirements." } }]}

Question 4

we control the goods quality in each production process

Accepted Answer

❓ How to solve if there is a quality problem? At Fanda Steel, we take quality issues seriously and are committed to resolving any concerns promptly and professionally. Our goal is to ensure your satisfaction while maintaining long-term trust. If you encounter any quality problem with our products, please follow this simple process: Step 1: Contact us immediately • Provide clear photos or videos showing the issue • Include the order number and product details (specification, batch number if available) Step 2: We respond within 24 hours • Our technical team will review your submission • We will analyze the root cause — whether it's a material, manufacturing, or handling issue • We will communicate our findings and proposed solution to you promptly Step 3: Resolution options Based on the evaluation, we will offer one or more of the following solutions: • 🔄 Replacement – We will arrange replacement products for the defective quantity • 💰 Credit – Issue a credit note for the value of the defective products • ↩️ Return – Accept return of the defective products (per contract terms) Our commitment to you: ✅ Every batch is inspected before shipment ✅ Mill Test Certificates (MTC) are available for all products ✅ Third-party inspections (SGS, BV, etc.) can be arranged upon request ✅ We value long-term relationships — we don't do one-off deals For any quality-related concerns, please contact our after-sales team directly. We are here to help. { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "How to solve if there is a quality problem?", "acceptedAnswer": { "@type": "Answer", "text": "At Fanda Steel, we resolve quality issues promptly. Customers should provide photos/videos and order details. We respond within 24 hours, analyze the root cause, and offer solutions: replacement, credit, or return per contract terms. Every batch is inspected before shipment, and MTC certificates are available. Third-party inspections (SGS, BV) can be arranged." } }]}

Question 5

we can supply the sample of corrugated steel roofing sheet

Accepted Answer

❓ Can you send the samples? Is the sample free? Yes, we provide samples for quality verification before you place a bulk order. Our sample policy is designed to be fair and flexible for different customer needs. 📋 Sample Policy: Sample Type Cost Shipping Refundable Small samples(cut pieces) ✅ Free Customer pays N/A Large samples(full sheets/tiles) 🔄 Charged Customer pays ✅ Refundable upon formal order Custom samples(made to your drawing) 🔄 Charged Customer pays ✅ Refundable upon formal order 🆓 What small samples include (free): Small cut pieces of galvanized/galvalume/prepainted steel coil Small pieces of corrugated roofing sheet Small samples of stone coated metal roof tiles Small samples of color coating (showing color and finish) 💵 What large samples include (charge applies): Full-size corrugated sheet (length as required) Complete stone coated metal roof tile Full guardrail beam section Any sample that requires production setup or uses full product size 📩 How to request a sample: 1. Contact our sales team with your product requirements and delivery address 2. We will confirm the sample availability, cost (if any), and shipping fee 3. Sample preparation: small samples in 3–5 days; large/custom samples in 7–15 days 4. Shipping: we arrange shipment and provide tracking information 📌 Important Notes: Sample shipping cost varies by destination, weight, and shipping method (courier, air, or sea) For large/custom samples, the sample fee is fully refundable once you place a formal order We can also send samples to your freight forwarder if you have one in China Multiple samples can be combined in one shipment to save on shipping costs 💡 We recommend ordering samples first to verify material quality, coating finish, color accuracy, and dimensional precision before committing to mass production. 📩 Contact us now to request your samples For urgent requests, let us know and we will expedite the process { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "Can you send the samples? Is the sample free?", "acceptedAnswer": { "@type": "Answer", "text": "Yes. Small samples (cut pieces) are free of charge, customer pays for shipping. Large samples and custom samples require payment, which is fully refundable upon formal order. Sample preparation: 3-5 days for small samples, 7-15 days for large/custom samples. We recommend ordering samples first to verify material quality, coating finish, and color accuracy." } }]}

Question 6

galvanized steel sheet in coil, aluminum zinc alloyed coated steel sheet in coil, prepainted steel coils

Accepted Answer

❓ What is the delivery time? Fanda Steel understands that timely delivery is critical for your projects. We offer flexible shipping schedules based on your order type and urgency. 📦 Standard Delivery Time: • Production orders: 30–35 days after receipt of deposit payment • Stock / ready goods: within 1 week ⏱️ Delivery Time for Special Orders: • Custom specifications or large orders: please contact our sales team for a confirmed shipping date • Sample orders: 7–10 days (depending on product and destination) 🚢 Shipping Methods: • Sea freight – most economical for bulk orders (20ft / 40ft container) • Air freight – available for urgent or small orders • Express courier – for sample shipments (DHL, FedEx, UPS) 📋 Order Process Timeline: Order confirmation 1–2 days Production 30–35 days (or 1 week for stock) Loading & shipping 3–5 days after completion We also offer: • Tracking information once the goods are shipped • All necessary shipping documents (Bill of Lading, Packing List, Invoice, Certificate of Origin, etc.) For urgent requirements, please contact us before ordering — we will do our best to accommodate your timeline. { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What is the delivery time?", "acceptedAnswer": { "@type": "Answer", "text": "Fanda Steel offers delivery within 30-35 days after deposit for production orders, or within 1 week for stock items. Custom orders and large quantities may require additional time. Sample orders: 7-10 days. Sea freight is most economical for bulk orders, while air freight and express courier (DHL/FedEx/UPS) are available for urgent or small shipments." } }]}

Question 7

we produce and export galvanized corrugated steel sheet, galvalume corrugated steel sheet, PPGI/PPGL corrugated steel sheet, stone coated metal roof tile

Accepted Answer

❓ Can you produce the roofing sheet according to the client's design drawing? Yes. Fanda Steel offers full customization for roofing sheets based on client drawings or physical samples. We understand that each project may have unique specifications, and our engineering team is experienced in translating your design requirements into finished products. 🛠️ Customization Options Available: Profile type – V-wave, U-wave, trapezoidal, sine wave, or custom profiles per your drawing Dimensions – thickness, width, length, and effective coverage to match your project needs Material options – galvanized steel (GI), galvalume (GL), or prepainted steel (PPGI/PPGL) Coating & color – zinc coating weight (Z20–Z275), PE or PVDF paint, RAL color matching Surface finish – smooth, embossed, or custom texture Punching & cutting – pre-punched holes or custom cut lengths as per installation requirements 📋 Minimum Order Quantity (MOQ): To make customization economical, we require a minimum quantity per design. The exact MOQ depends on the complexity of the profile and the material specifications. We recommend contacting our sales team with your drawing and estimated quantity for a confirmed quotation. 📄 What we need from you: • PDF or CAD drawing of the profile • Material specifications (thickness, coating, color, etc.) • Estimated quantity to determine feasibility and pricing ⏱️ Typical lead time for custom orders: 30–45 days after sample/drawing approval (depending on complexity). 🌍 We have extensive experience manufacturing customized roofing sheets for projects across Southeast Asia, Africa, the Middle East, and South America. No design is too complex for our team. 📩 Contact us with your drawing and specifications for a free consultation { "@context": "https://schema.org" rel="nofollow"https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "Can you produce the roofing sheet according to the client's design drawing?", "acceptedAnswer": { "@type": "Answer", "text": "Yes. Fanda Steel offers full customization for roofing sheets based on client drawings or samples. Customization options include: profile type (V-wave, U-wave, trapezoidal, sine wave), dimensions, material (GI/GL/PPGI), coating weight, PE/PVDF colors, surface finish, and pre-punched holes. MOQ depends on design complexity. Lead time: 30-45 days after approval." } }]}

Question 8

we produce and export galvanized steel sheet in coil, aluzinc steel sheet in coil, color steel coils

Accepted Answer

❓ Do you have quality certifications? Yes. Fanda Steel maintains strict quality control standards and holds recognized certifications to ensure product reliability. Our quality assurance system covers every stage — from raw material sourcing to final product delivery. Here is what we offer to guarantee the quality of your order: 📋 International Standards Compliance: Standard Applicable Products Region ASTM Steel coils & structural products USA & Americas JIS Steel coils & sheets Japan & Asia EN Steel coils & construction materials Europe GB/T All products (Chinese national standard) China & global 📄 Certifications & Documentation Available: Mill Test Certificates (MTC) – provided with every batch, showing chemical composition and mechanical properties Inspection Reports – thickness, coating weight, surface quality, and dimensional accuracy Material Traceability – full traceability from coil to finished product Certificate of Origin – for customs clearance in your country 🔍 Third-Party Inspection: We welcome independent quality verification. The following inspection agencies can be arranged upon request: SGS – comprehensive product inspection and testing BV (Bureau Veritas) – quality assurance and compliance verification Intertek – product certification and testing Other agencies – as specified by your requirements 🔬 Our Quality Control Process: 1. Raw material inspection – chemical composition and physical properties verified 2. In-process inspection – continuous monitoring during production 3. Final inspection – full dimensional and appearance check before packaging 4. Pre-shipment inspection – random sampling and testing ✅ Quality Guarantee: All products are backed by our quality commitment. If the product does not meet the agreed specifications, we will replace it or provide a credit in accordance with our quality assurance policy. 📩 Contact our quality team for specific certification requirements or inspection arrangements { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "Do you have quality certifications?", "acceptedAnswer": { "@type": "Answer", "text": "Yes. Fanda Steel's products comply with ASTM, JIS, EN, and GB/T international standards. Mill Test Certificates are available per batch. Third-party inspections (SGS, BV, Intertek, etc.) can be arranged upon request. Our quality control process includes raw material inspection, in-process monitoring, final inspection, and pre-shipment testing. All products are backed by our quality guarantee." } }]}

Question 9

we produce and export galvanized steel coil, galvalume steel coil, corrugated steel roofing sheet, color steel coils

Accepted Answer

❓ What payment methods do you accept? Fanda Steel offers flexible and secure payment options to accommodate different customer requirements and project scales. We work with clients worldwide and understand the importance of safe, transparent transactions. 💳 We accept the following payment methods: 1. T/T (Telegraphic Transfer) – Recommended for most orders Price Term Payment Schedule FOB / EXW 30% deposit in advance + 70% balance before shipment CIF / CFR 30% deposit in advance + 70% balance against copy of Bill of Lading 2. L/C at Sight (100% Irrevocable) • Secure and widely used for large-value orders • Confirmed by a reputable bank • Suitable for government tenders and large-scale projects 📋 Factors that may affect payment terms: • Order value and quantity • Cooperation history with Fanda Steel • Destination country and specific requirements • Product type (standard stock items vs. custom orders) 🏦 Banking Information: All banking details, including beneficiary name, account number, SWIFT/BIC code, and bank address, will be provided on our Proforma Invoice or Sales Contract. 💡 What we recommend: For first-time cooperation, we typically suggest T/T with 30% deposit, which balances security for both parties. For ongoing partnerships, we are open to negotiating more flexible terms. 📩 Contact our sales team to discuss payment terms for your specific order { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What payment methods do you accept?", "acceptedAnswer": { "@type": "Answer", "text": "Fanda Steel accepts T/T and 100% L/C at sight. For T/T: 30% deposit in advance + 70% balance before shipment (FOB/EXW) or against B/L copy (CIF/CFR). L/C at sight is recommended for large orders. Payment terms may vary based on order value, cooperation history, destination country, and product type." } }]}

Question 10

we produce and export galvanized steel coil, aluzinc steel coil, ppgi/ppgl steel coil, corrugated steel sheet

Accepted Answer

❓ What is the MOQ for galvanized steel coil, galvalume steel coil, and prepainted steel coil? The MOQ (Minimum Order Quantity) for steel coils depends on production efficiency, shipping logistics, and cost-effectiveness. Here is our standard guideline: 📦 Standard MOQ: One roll = approx. 16–18 tons (standard coil weight) One 20ft container = approx. 25–27 tons (6–9 coils per container) Recommended MOQ: 2 containers (approx. 50–54 tons) for the most cost-effective shipping and production scheduling 💡 Why we recommend 2 containers: Factor Explanation Shipping cost Per-ton freight cost is lower with full container load Production efficiency Better utilization of production line setup time Quality consistency Same batch ensures uniform coating and thickness Cost-effectiveness Reduces handling and documentation costs per order 🔄 Flexible options for different needs: Trial orders – Smaller quantities (e.g., 1 roll) can be arranged upon request, but may incur higher per-ton costs Sample orders – Small samples (cut pieces) are available for quality verification Stock orders – If stock is available, smaller quantities can be shipped immediately 📌 Additional notes: • MOQ may vary for custom specifications (different thickness, coating, or color) • Combining multiple products in one container is possible to meet your project needs • For urgent or smaller requirements, please contact our sales team for a customized solution 📩 Contact us for a tailored quotation based on your specific requirements { "@context": "https://schema.org" rel="nofollow"https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What is the MOQ for galvanized steel coil, galvalume steel coil, and prepainted steel coil?", "acceptedAnswer": { "@type": "Answer", "text": "Standard MOQ: one roll = 16-18 tons, one 20ft container = 25-27 tons. Recommended MOQ is 2 containers for best cost-effectiveness. Trial orders (1 roll) and sample orders available upon request. Combining multiple products in one container is possible. MOQ may vary for custom specifications." } }]}

Question 11

We produce and export galvanized steel coil, galvalume steel coil, ppgi/ppgl steel coil

Accepted Answer

❓ Are you a manufacturer or trade company? We are both – an integrated manufacturing and trading company. This unique combination gives you the best of both worlds: factory-direct quality and pricing, plus professional trading capabilities for seamless export and logistics. 🏭 Our Own Production Lines: ✅ Galvanized steel coils (GI) In-house production ✅ Galvalume steel coils (GL) In-house production ✅ Prepainted steel coils (PPGI/PPGL) In-house production ✅ Corrugated steel roofing sheets In-house production ✅ Highway guardrail systems In-house production 💡 Why this matters to you: Factory-direct pricing – no middleman markup Quality control – we monitor every step of production Flexible customization – faster response to your specific requirements Reliable supply – we control our production schedule Direct communication – you talk to the people who make the products Beyond our own factory production, we also offer: • Complete accessory supply (guardrail fittings, bolts, spacer blocks, etc.) • Professional export documentation and logistics • One-stop sourcing for your entire project With over 15 years of industry experience, we combine manufacturing strength with trading expertise to deliver quality products and reliable service to customers worldwide. ✈️ Welcome to visit our factory – contact us to arrange a tour { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "Are you a manufacturer or trade company?", "acceptedAnswer": { "@type": "Answer", "text": "We are both an integrated manufacturing and trading company. We have our own factory for galvanized steel coils, galvalume steel coils, prepainted steel coils, corrugated steel roofing sheets, and highway guardrail systems. This gives us factory-direct pricing, quality control, flexible customization, reliable supply, and direct communication. We also offer export logistics and one-stop sourcing services." } }]}

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