1. Is there a clear prohibition against mixing different materials of galvanized coils in warehousing?
A: According to industry-standard warehousing practices, galvanized coils of different specifications and varieties do need to be stacked separately. However, the wording is usually not an absolute prohibition, but rather a mandatory requirement of "should be stacked separately." Based on the principles of hot-dip galvanized steel stacking, under the condition of stable stacking and ensuring safety, materials must be stacked according to variety and specification, with different varieties stacked separately to prevent confusion and cross-corrosion. Storage regulations for color-coated galvanized steel coils also clearly state that different types of color-coated galvanized steel coils should be stacked separately to avoid confusion and contact corrosion. For cold-rolled and hot-rolled galvanized coils, it is recommended in warehousing practice to place them separately with a distance of no less than 1 meter. Therefore, although there is no uniform regulation that "absolutely prohibits" mixing all materials, warehousing practice and industry standards clearly require the separate stacking of galvanized coils of different materials.
2. What are the actual hazards of storing galvanized coils of different materials together?
A: Mixing them together mainly poses two risks: confusion and corrosion. The risk of confusion manifests in warehouse management-galvanized coils of different materials have significantly different properties. For example, the mechanical properties of general-purpose coils and deep-drawing galvanized sheets are completely different. If they are mixed and confused during subsequent handling, it may directly lead to the scrapping of downstream processed products. The risk of corrosion is more insidious. When two metals with different electrochemical potentials come into contact in a humid environment, they form a galvanic corrosion cell, where the metal acting as the anode will accelerate corrosion. For example, if ordinary galvanized coils are in direct contact with stainless steel galvanized coils in a humid environment, the galvanized coil substrate with the lower potential is more likely to lose its zinc layer protection, leading to accelerated corrosion. Furthermore, if residual substances such as acids, alkalis, salts, or cement are mixed into the surface of the galvanized coils, which can corrode the zinc layer, or if the surfaces are damaged by direct friction due to mixing, the quality of the zinc layer will deteriorate.
3. Are the corrosion risks the same for different types of galvanized coils? Which combinations require special attention?
A: Even among products classified as "galvanized coils," the corrosion risks are not uniform. Pure zinc coatings generally do not experience significant accelerated corrosion, as zinc-to-zinc contact is electrochemically compatible. However, the combination of different zinc-based coatings with other materials varies. Experience shows that when galvanized layers come into contact with metals such as copper, brass, and lead in humid environments, the galvanized layer will corrode rapidly. Secondly, when galvanized coils are in direct contact with stainless steel and have a conductive circuit and electrolyte, the potential difference can trigger galvanic corrosion, which must be prevented through physical isolation. Furthermore, if the storage environment contains chemicals such as ammonium chloride, salt, or chlorides, they can easily damage the zinc coating; therefore, mixed storage or spillage should be strictly avoided. For galvanized coils with significant differences in production processes (hot-dip galvanizing and electro-galvanizing), strength grades, and surface treatments, it is generally recommended to store them separately for management purposes to prevent confusion.
4. What protective measures should be taken when galvanized coils of different materials must be stored in the same warehouse?
A: When storage conditions are limited and galvanized coils of different materials must be stored in the same area, the following protective measures should be taken: Physical isolation is the primary method. For two metal materials with significantly different potentials, nylon gaskets, rubber pads, or insulating tape can be used to separate them, blocking the current path and thus preventing galvanic corrosion. The bottom of the galvanized coils should be raised with wooden or rubber blocks to prevent moisture, generally at least 15 cm high, and direct contact with the ground should be avoided. When stacking, different types (materials with different performance and alloy compositions) must be strictly separated. In addition, it is recommended to leave a passage of at least 0.5 meters between stacks of different batches for easy daily inspection and management. For situations where a humid environment may accelerate zinc discoloration, warehouse humidity should be strictly controlled (relative humidity is recommended not to exceed 70%), and temperature should be monitored.
5. How to correctly distinguish and label galvanized coils of different materials in actual storage management?
A: The key to scientific warehouse management lies in a sound classification, labeling, and recording system. First, fixed storage areas should be designated according to variety (commercial grade, stamping grade, structural grade, etc.) and specifications (thickness, width, zinc layer weight), and clear material labels should be hung or affixed to each stack. During the receiving process, stacking should be strictly carried out according to the receiving order, and a material ledger should be established to implement the "first-in, first-out" principle. At the same time, to avoid confusion, the grade, standard, and batch number information are also marked on the raw materials of the galvanized coils' factory packaging; warehouse managers must carefully check the materials upon receipt and should not judge the material solely based on appearance, color, or surface condition. Furthermore, the surface condition of the galvanized coils in storage should be inspected regularly. If abnormalities such as zinc layer discoloration or white rust spots are found due to mixed storage or environmental factors, they should be isolated and treated promptly, and any possible mixed storage or management oversights should be investigated. Through the above-mentioned standardized management, not only can material confusion be prevented, but the usability period of galvanized coils in the warehouse can also be greatly extended, meeting the goal of ASTM A123 standard that reasonable storage can "extend the life of galvanized parts by 3 to 5 years".