NIPPON STEEL CORPORATION

Precautions

Precautions for use

Use underwater or in flowing water

 In applications underwater or with frequent exposure to flowing water, the stable protective film layer that is characteristic of ZAM® is difficult to form, so that sometimes ZAM® may gather red rust early without showing superiority to hot-dip zinc-coated steel sheets. Be aware of this when using it in such applications.

Handling

・In order not to damage the coating surface, handle the product carefully and do not put any sweat or finger smudges on the surface.
・If the surface should become damaged, repair it.
・ Be careful when removing a coil band because the end of the coil could spring up as it unwinds.
・ Store products securely, so that coils do not tip over and stacked-up cut sheets do not topple.
・ Be careful to prevent water stains and dew condensation. If packaging paper is damaged, repair it.

Processing

・If the surface is damaged during processing, it could adversely affect corrosion resistance and paintability. In particular, some types of lubricating oil may corrode the coating layer during press working. It is therefore necessary to check the type of lubricating oil to be used. When lubricant is used, perform degreasing or other post-treatment after the processing.
・As time passes, a steel sheet tends to harden, resulting in a decrease in workability. To avoid this, use the steel sheet as soon as possible.

Precautions to prevent galvanic corrosion

(1) Avoid direct contact with lead or copper (or copper ion drops)
(2) For metal fittings and attachments, use products made of stainless steel (SUS304) or aluminum or those which are painted or heavily coated with zinc for increased durability.
(3) When using ZAM® in a salt-damaged or snow-covered area, use metal fittings and attachments made of a similar metal (aluminum, zinc-coated metal) or stainless steel insulated properly and treated with an anticorrosive (or a sealing material)
(4) In such applications as lightning conductors where corrosion is likely to occur, insulation tape or aluminum wire should be used.
(Source: Preventive measures of bimetallic corrosion of prepainted/zinc-based coated steel sheets: Hot-dip zinc-coated Committee, The Japan Iron & Steel Federation)

Precautions to prevent corrosion due to
contact with a preservative-treated or
termite resistant wood

ZAM® should not be left in contact with wood containing preservative/ant repellant for an extended period of time. Wood and laminated wood treated with preservatives and ant-repellants (primarily copper-based agents) adversely affect corrosion resistance property of coated steel sheets and prepainted steel sheets. Therefore, where these steel sheets are likely to come in contact with wood materials (parts of the roofs including eaves, roof edges and joints for example), insulation underthatch (roofing stock or butyl tape) should be used for rust prevention and steel-wood direct contact should be avoided.
(Source: Preventive measures of bimetallic corrosion of prepainted/zinc-based coated steel sheets: Hot-dip zinc-coated Committee, The Japan Iron & Steel Federation.)

Welding

・When conducting resistance welding, proper care should be taken of the electrodes to remove zinc pickups.
・For coated steel sheets containing ZAM® , coatings evaporate due to heat from welding, so that greater amounts of sputtering and fume are generated than in the case of hot- or cold-rolled steel sheets. Take appropriate safety measures at the time of welding work.

<Safety measures for welding hot-dip zinc-coated steel sheets>
When welding hot-dip zinc-coated steel sheets, in addition to such common welding hazards as electrification, damage to the eyes caused by arc ray, burn caused by contact with hot objects and fire, be careful of;
 1. increase in volume of fume generated by evaporating zinc, and
 2. burns or fires due to larger volumes of spatters generated.
Especially, since fume is inevitable when welding hot-dip zinc-coated steel sheets, proper measures should be put in place. Health hazards of zinc are shown in the table.

Effects of zinc on the human body

Item Effect
Carcinogenicity Has not been confirmed at the present time
Acute toxicity It is known that inhaling a large quantity of zinc fumes results in a fever several hours later (zinc fume fever). The affected personrecovers naturally in about 24 hours. The mechanism by which this occurs is not understood.
Chronic toxicity No evidence has been found that zinc causes symptoms of chronic toxicity.
Other effects Zinc deficiency can cause delayed growth, reduced functioning of the gonads, depression, loss of appetite, and other symptoms.
Zinc, which is present in the human body in greater quantity than any other [metal] element except iron, which is an important essential element. Its harmfulness is thought to be low provided that protective measures are taken and a large quantity is not ingested.
Source : Osamu Wada, “Metals and Man : Ecotoxicology and Clinical Practice,” published by Asakura Shoten (1985)

Guide to ordering

Material, coating weight, chemical conversion treatment, oiling

・Select steel grade, coating weight, and chemical treatment to fit your application. Apart from the type of chemical treatment, you can choose either antirust oiling or no oiling. Oiling is recommended to minimize lubrication during press processing, soiling, and scratching. Oiling is necessary when no treatment is made.

Size

・Design according to the production range described in this catalog. Contact us beforehand if your conditions for use require more stringent specifications. Please consult us for sizes outside the range.

Product Shapes

・Choose either mill edge or slit edge according to your application. Also, choose either coils or cut sheets according to your cutting and processing conditions. From the standpoint of promoting continuous, automated operations and optimizing yield, it is recommended to use coils. When using coils, be aware that sometimes defective parts may be mixed in (because such parts cannot be removed by the inspection).

Inside diameter and outside diameter

・In the case of coils, specify the inside diameter and outside diameter to fit the specifications of your equipment. In specifying the inside diameter, allow for possible buckling in inner laps of the coil depending on the sheet thickness.

Packing mass

・Specify the packing mass according to handling capacity, etc. For coils, specify the maximum mass (if necessary, the minimum unit mass). The greater the mass, the easier the operation will be.

Applications and processing methods

・Quality control better suited to your application and processing method can be applied if relevant information is timely provided.

Phenomenon of darkening of hot-dip zinc-based coating

Overview

・It is known that with the passage of time, hot-dip zinc-coated steel sheets are subject to what is called darkening, namely, decrease in surface glossiness. ZAM
ZAM® may also suffer discoloration as with other hot-dip zinc-based alloy coated steel sheets.

What is darkening?

・Darkening is a phenomenon in which the steel sheet appears gray due to the presence of a very thin oxide film on the zinc surface layer. In hot-dip hot-dip zinc-coated steel sheets, a very thin oxide film whose principal component is ZnO is formed on the zinc coating surface layer even immediately after manufacturing, and it has the property of changing and growing as time passes. From our experience to date, we infer that this phenomenon of darkening occurs by the following mechanism.
① An oxide film grows

② The structure and thickness of the oxide film change

③ The changed state of ② causes a change in the optical absorption coefficient

④ The surface takes on a gray appearance