Best Practices for Handling, Storage and Use of Galvanized Products

Best Practices for Handling, Storage and Use of Galvanized Products

Handling and Storage

1. The steel manufacturer needs to apply the chemical treatment and/or oil in the specified manner to cover the entire surface area of the sheet. It may be noted:

Lubricated strips and sheets have a low friction coefficient and slide easily. Coils may collapse (telescope, etc.) due to repeated uncoiling and recoiling. Cut sheets in piles may slide due to impact. Use carefully in handling and work around storage areas.


2. When possible or required, wrap the coils with either paper or plastic that is specially made for this application. 


3. When receiving product, check for moisture in the package. Dry immediately if wet.


4. Repair broken packaging if long-term storage is required. Abrasion marks (black dents) may occur due to pressure if transportation or if transportation or storage conditions are improper.


5. The shipper needs to protect the steel during shipment to the customer’s plant. Even if the coils/bundles are wrapped, ship only in covered watertight conveyances. If it is necessary to use an uncovered conveyance, wrap the load completely with a tarp to assure no water intrusion if it rains during shipment. Avoid tearing the paper. 


6. The best practice is to store coils in a climate-controlled warehouse. Use the material promptly. Whenever possible, do not allow the product to remain in storage for extended periods of time (in excess of two months). Storing galvanized coils in unheated warehouses over the winter in the northern U.S.A or Canada or North Europe/Asia carries the risk of condensation forming between the laps due to sudden temperature drops after a warm period. This can occur even when the coils are paper wrapped and encased inside metal shipping shrouds. In this circumstance, white rust can form after a few weeks, even on well-passivated sheet. Even in climate controlled warehouses there is a risk of condensation forming on between laps if cold steel is brought in below the dew point temperature in the storage area. 


7. For shipping from the manufacturing plant to the final location, the product again needs to be protected, especially if sheets/parts are in intimate contact with each other. When this is the case, the product is very susceptible to storage stain, as the zinc surfaces will not dry properly if they get wet.


8. Paper wrapping is one way to protect the sheets while in transit or during storage at a jobsite. Be careful to not wrap the bundle if the sheets are wet. This traps moisture in the bundle and prevents drying. 


9. If bundles of galvanized sheets or blanks get wet, the only way of preventing or minimizing storage stain is to immediately separate all the pieces so they can individually dry. Unfortunately, if the material is unpassivated, it may be too late, as storage staining will occur immediately after becoming wet. 


10. Do not wrap the sheets tightly in plastic. Allow the product to “breathe” by providing air circulation


11. If outdoor storage is unavoidable, place bundles above ground by at least 12 inches to allow air circulation underneath. If bundles are stacked, ensure free circulation of air between bundles using cured lumber spacers. 


12. Inspect frequently to assure that the panels have not become wet. 


13. Elevate one end of a bundle of sheets to allow water to drain if moisture gets between the sheets. Make sure there are no low spots along the length so as to allow water to flow freely if necessary. If bundles have been found to be wet, separate all the sheets immediately.


14. When shipping manufactured parts or storing them outdoors, they must be dry and free of roll or press forming lubricants and protected from the weather. If not protected from the weather, then each part should be ‘free standing’ (not touching other parts), with any concave parts being placed so the concave side is down and not able to collect water.


15. Steel sheet products have sharp edges. Handle carefully using gloves to avoid injury.

Using Galvanized Steel for painting:

The substrates of application are usually the Zn-coated steels with oiling. It should wait for painting on the cleaned substrate surfaces after the overall chemical passivation reaction with chemical medicament is produced.  The passivated films can keep the paints from directly contacting with active metals, and have long-term stability to protect the products. Common chemical treatment is phosphate-zinc treatment. The densely phosphate-zinc crystals can improve the adhesion between the primer and the substrate. 

Factors causing painting defects:

1. Scratches and oil stain due to improper handling can result in paint defects.


2. Some types of lubricating oil erode zinc. Prior testing before using may be recommended


3. Insufficient degreasing can cause paint defects.


4. Degreasing by spraying or dipping in a neutral or low alkaline agent is recommended. Strong alkaline agents can damage the surface.


5. Adequate rinsing after degreasing is recommended. If degreasing is inadequate, water repulsion can be observed on the strip after dipping in clean water. Use a degreasing method which maintains a smooth and uniform water film. 

6. Dirt or other foreign matter on the surface will cause paint defects. Degrease adequately before painting. These foreign matters may cause the paint to be unable to bond to the substrate surfaces, and may result in declining to fail the adhesion of film. Galvanized steel products are chemically treated to improve paint adhesion. However, certain paints may have poor adhesion with certain zinc coatings. Prior testing is recommended. If the passivation film of chemical treatment is not sufficient or uneven, once outside corrosion factors are contacted with metal, the reactive metal is very easy to oxidize. Then oxide will thoroughly destroy the adhesion of primer paint to the steel surface. Moreover, if there are loose passivation films and coarse crystals or the residue contamination on the chemical treatment liquid, it will also cause the deficiency of the film adhesion. Undercoating with a wash primer will help ensure good results.

Avoiding stretcher strain and Aging

There are solid solution Carbon and Nitrogen in the low carbon steels. If they are not treated properly, the stretcher strain marks will be occurred in the process. 


Therefore, the temper rolling process needs to be carried out appropriately on these products to eliminate the extension of yield point. However, the extension of yield point may appear again with the longer period of storage as we called the aging problem. Aging is mainly related to solid solution Carbon, storing temperature and time. 


The first in, first out (FIFO) inventory management to use these grades of steel is recommended as soon as possible in order to avoid the aging problems.

Avoiding Decontamination of film treatment coils after processing

The surfaces of Zn-coated steel sheets are often treated with anti-finger print as a temporary antirust treatment. Such steel materials will again be degreased, decontaminated, rust removed and cleaned, and film antirust treated after processing. Since these treatments may cause discoloration and damages on the film of steel surface, the operations toward to the lower concentration of medicament, the lower processing temperature, and shorter processing time will be advantageous. Concrete recommendations are as follows:

a. The pH of degreasing liquid is recommended as 7.0 pH to 10.0 pH. It should be done close to the room temperature and not take much time to treat degreasing liquid. 

b. Please use the non-polar solvents to clean samples and graze it slightly. Do not use the polar organic solvents.

c. If the products are needed to dry, the drying temperature and time are maximum 180 degree Celsius and maximum 15 minutes respectively.

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