Storage and Handling Advice’s

UNICOIL products are manufactured according to the highest national and international Quality Standards practiced in Metal and Organic Coating Industry followed by Best Practices in Packaging and shipping.  While Unicoil’s responsibility ends by delivering the products in good condition, it realizes that damages can take place if proper care is not taken during handling and storage, after receipt by its customers.  To derive the maximum benefit by its customers, UNICOIL formulated the guidelines/best practices for Handling and storage of Pre-Painted Galvanized Steel Coils and sheets. The goal is to eliminate avoidable problems and reduce the need for additional work and material loss.

Two important elements to be avoided during Handling and Storage of Galvanized Steel sheets and Coils:

• Physical Damage
• Coil Collapse
• Dents/horse shoe marks
• Warpage of Sheets
• Surface Scratches
• Degradation of Coating
• Blistering and Paint delamination

Guidelines for preventing Physical Damage for Coils:

• As the Organic film coated on the Galvanized steel is soft, Pre- Painted Galvanized Steel Coils are supplied with Bore Vertical form (Eye to the Sky). This is the most preferred form for delivery of Pre-Painted Galvanized Steel Coils to avoid coil collapse/physical damage.
• However, Pre-Painted Galvanized steel coils of width >600mm are supplied in Bore Horizontal Condition, only on request, which is a less preferred form for delivery.
• In both cases of bore vertical and bore horizontal forms, the coils are supplied on wooden pallets for delivery (except for the breakbulk shipment – coils are supplied bore horizontal form without pallet.). Fig 1a,b
• For coils received in brake bulk, without pallets, it is advised to use purpose-made stillages with coil contact points which are either wooden, rubber or covered in felt. The coil contact surfaces should usually form a V-shape to hold the coil.
• Single row Coil stacking is mandatory for Bore Horizontal coils to avoid Coil Collapse and possibilities of Dents.
• For Bore Vertical Coils two-hi coil stacking is allowed subject to following.

Fig 1 a ,b Securely Packed Pre-Painted Galvanized Steel coil with Bore Vertical and Bore Horizontal with wooden pallets

Pre-Painted Galvanized Steel Coils should always be stored on a stable, clean, dry, flat and level surface to avoid possibilities of coil tilting and falling.

Fig 2 a ,b Pre-Painted Galvanized Steel coil  to be stored on flat, level surface

• For Two – High stacking the maximum height of the stack, for >600mm wide coils, should not exceed 3mtrs.
• Coils should be stacked centrally above each other to avoid accidental fall of coil.

Smaller weight coils (lower outer diameter coils) to be placed on top of Bigger weight coils (Higher Outer diameter coils),

Fig 3 a ,b Pre-Painted Galvanized Steel coils stacking centrally above each other

Fig 4 a ,b Smaller weight coils over the Bigger Weight coils

• The distance between two rows of coils, especially in a single stack bore horizontal coils should be adequate to avoid unintentional damage by the lifting tackles.
• Proper care is to be taken while lifting the bore vertical coils, with the fork lift to avoid physical damages.
• For the purpose of loading the   bore vertical Pre-Painted Galvanized Coils onto the intended processing equipment, it is essential to tilt the coil axis from bore vertical to bore horizontal.
• To prevent dents, horse shoe marks and physical damage of coils that develop due to unscientific methods of tilting the axis of bore vertical coils to bore horizontal axis,  it is strongly recommended to use a Coil Tipper which is also known as Upender for tilting the bore vertical coils.  Fig 5a,b
• The coil tipper/upender of suitable capacity is to be used. Mechanical or Electro Mechanical or Hydraulically operated Coil tippers are recommended.

Fig 5 a ,b  Coil Tipper/Upender for tilting the axis of Bore vertical coil to Bore Horizontal

Guidelines for preventing Physical Damage for Sheets:

• Pre-Painted coils are usually roll formed by customer and cut into length in sheet form.
• Such sheets are to be piled uniformly without any zig zag pattern and are to be securely strapped into a bundle to avoid damages. (Fig 6.
• Such bundles are  stored in multiple stacks before delivering to the installation site
• Dunnage of Hard wood should be placed between individual bundles to facilitate lifting.
• Dunnage should be symmetrical and of sufficient size to allow safe use of lifting/handling gear. A minimum cross section of 60mmx60mm hard wood dunnage is recommended.
• It is recommended to place the dunnage in the transverse direction.

Recommended dunnage spacing is around 900mm as shown

Fig 6  Piling of Roll formed sheets                                                                            Fig 7  Recommended dunnage spacing in transverse direction

• Following precautions are to be taken for multiple stacking of bundles to avoid warpage/damage to the pre-painted galvanized steel sheets.
• To ensure the stack stability, the stack height should be limited. For sheets of >600mm width and length of >1000mm, the max stack height should be limited to 1500mm.

As far as possible, stack bundles of same dimensions. The bundles should be aligned properly as shown

Figure 8a Bundles should be stacked with proper alignment and matching dimensions; Figure 8b misaligned bundles can cause warpage and damage; Figure 8c stacking longer bundles on shorter lead to warpage/damage. 

Use certified web slings for handling the bundles by crane. Do not use steel wire ropes/Chains as shown

Fig 9 a,b Use certified web slings for lifting by crane, not steel wire ropes/Chains

Use Steel Beams to lift bundles of more than 4mtr length, by crane as shown in figure below to avoid warpage of sheets. Do not use belts in an obtuse angle and do not choke the material to avoid damage.

Fig 10 a,b Use Steel beams to lift bundles of more than 4 mtr length. Do not use belts in Obtuse angle.

Use Fork lift to lift bundles of less than 4 mtrs length as shown  to avoid warpage of sheets.

Fig 11 Use Forklift to lift bundles of less than 4mtr length

Pre-Painted Galvanized steel sheet bundles should be stored flat on level ground and in a covered Shed.

Fig 12  Store bundles flat on level ground in a covered shed

To avoid surface scratches while lifting sheets from the bundle, lift the sheet from both sides and not from one side as shown below.

Fig 13 a,b   Lift sheets from both sides and not from one side to avoid scratches

• AS THE BUNDLES ARE DELIVERED FROM CUSTOMER WAREHOUSE TO INSTALLATION SITE AND STORED BEFORE INSTALLATION,, SAME GUIDELINES ARE RECOMMENDED FOR HANDLING AND STORAGE, TO AVOID PHYSICAL DAMAGE TO THE PRE-PAINTED GALVANIZED SHEETS.

Reasons for Degradation of Coating:

Quality system at UNICOIL ensures that the pre-painted Galvanized steel is manufactured and tested to comply with all mandatory requirements of the relevant national and international standards to ensure long-term durability of the product before delivery.

Pre-Painted galvanized steel coils are usually roll formed by customer, cut into length and stored in sheet form before delivering to the site.

Care is to be exercised during roll forming to avoid formation of cracks on the paint film by following the best practices of roll forming.

Product deterioration can take place if proper care is not taken during storage of the Pre-Painted Galvanized steel coils/sheets, both at customer warehouse and installation site, after it is delivered from the customer warehouse.

Blistering/Paint film delamination are the two commonly observed problems due to poor storage practices.

• It can occur when sheets of Pre-Painted Galvanized sheets that are in close contact (in a coil or stacked bundles) get wet either by Direct Water intrusion or condensation between the surfaces.
• Rapid temperature changes may induce condensation between coil wraps/sheets or panels.
• As Paint film is not impervious, when there is ingress of moisture or water between the wraps of Pre-Painted Galvanized steel, the water reacts with the zinc coating.
• The reaction of zinc with moisture in the absence of free air circulation leads to corrosion products leading to blistering and loss of adhesion/delamination between the galvanized steel surface and the paint film. Typical blistering and delamination of paint is shown in the figure 14a – Blisters, 14 b&c Delamination of Paint film
• Any cracks in the paint film during the roll forming process can aggravate the reaction.

Fig 14 a,b,c: a – Blisters   b&C  Delamination of Paint film from the Galvanized steel surface

In cases of prolonged storage, with water ingress,   the corrosion of base steel can take place showing Red rust after delamination of paint film.  Such complete corrosion of zinc coating can take place, showing Red-rust even before installation of the product.  A typical corrosion of base metal is shown

Fig 15 Typical corrosion of base metal of a Pre-Painted Galvanized Steel

Guidelines for preventing Coating Degradation:

• Main Recommendations are

Store inside/under covered shed

The best way to ensure coils/sheets keep their initial aspect and properties is to store them inside, under a covered shed as shown

Fig 16 a,b   Storage of Pre-Painted Galvanized Steel coils on pallets in a covered shed

Keep Dry :

• If the coils/sheets cannot be stored inside, specific care should be taken to ensure they remain dry.
• Cover with polyethylene/plastic/tarpaulin sheet to protect from rain.
• In case of sheets Store on levelled ground at a slope of 3 to 5° for easy draining of water in case of rain water ingression. Fig 17
• If rain water ingress is suspected, separate the sheets as quickly as possible and wipe & dry and use as quickly as possible.
• In case of coils to be stored in open area, store the coils on pallets to avoid water ingress into the bottom portion of the coil and cover with polyethylene/plastic/tarpaulin sheet to protect from rain.
• Provide good ventilation to avoid build-up of moisture between coil wraps/bundle wraps

Fig 17 Store sheets on levelled ground at a slope of 3 to 5°

• Avoid Condensation
• Best practice is to store coils/sheets in a room kept at a constant temperature with good ventilation.
• If the above cannot be followed, avoid sudden temperature changes, especially in humid conditions, while moving coils/sheets from unheated warehouse at a temperature of Zero Deg.C to a heated area, around 20 Deg.c temperature areas.
• Additional care is recommended if the product is applied with protective film as the protective film reduces the ability for the pre-painted coatings to breathe.

• Inspect the storage site:
• Inspect the storage site, especially when stored outside in open area,  for any damages to packing and to ensure water/moisture has not penetrated the bundles/coils.

• Use Promptly:
• The physical characteristics of paint film, such as pencil hardness, T-bend and impact resistance change overtime,  it is recommended that the coils/sheets are used quickly, following FIFO (First in First out)..
• UNICOIL recommends maximum storage time of six months from the date of delivery.
• In case the product is delivered with protective film, UNICOIL recommends maximum storage of three months from the date of delivery, to avoid the chance of adhesive residues sticking to the paint.
• ^{Protective film applied on the panel, by panel manufacturer (UNICOIL customer) must be removed at the time the panel is installed. If this film is not removed by the installer at the time of installation, the heat and environment will “bake” this film onto the panel and it will be difficult, if not impossible, to remove. It will eventually peel, discolour, and become an eyesore.  The period between the panel production and installation should be as low as possible and experience shows, longer periods of more than 60 days in removal of protective film leads to the problem of peeling/discoloration. It is suggested that the panel manufacturer should advise his customer accordingly.}

                          REPORT RECEIPT OF PRE-PAINTD GALAVANIZED COILS/SHEETS WITH DAMAGES TO PACKING/ WETTING OF  COILS/COLLAPSE OF COILS PROMPTLY WITHIN MAXIMUM THREE WORKING DAYS FROM THE DATE OF RECEIPT ALONG WITH DELIVERY DETAILS AND IDENTIFICATION DETAILS OF COIL/PACKET ALONG WITH PHOTOGRAPHS FOR PROMPT RESPONSE.