Thin Organic Precoatings
|Publication Date:||1 August 2007|
This standard covers the requirements for organic precoatings applied to a hot dip coated or electrolytical galvanized sheet steel substrate. The substrate may be cold or hot rolled sheet steel.
Thin organic precoatings serve to improve the corrosion protection of flanges and contact faces which cannot at all or only insufficiently be protected from corrosion by secondary measures such as E-coating, application of hem flange sealants or cavity waxing.
Thin organic precoatings are applied on zinc plated coil material by no-rinse technique. To improve the adhesion, usually chromium-free adhesion promoters are used. The organic precoating itself can be based on different polymer systems like epoxy, polyurethane, polyacryl or polyester. The weldability is guaranteed by pigments.
At present time, thin organic precoatings are not used for outer surfaces because of paint appearance aspects.
Organic Precoatings (OP) on zinc-plated substrates are specified by OP added to the basic specification number. The first identification designates the organic precoating on the inner, the second identification on the outer side. Differentially coated products may be specified. The products, which shall be used as organic precoating and adhesion promoter - just as their coating thicknesses/masses -are described by type codes (see Section 8).
Zinc-plated steel grades shall be used as base material for organic precoatings (coatings, see 184.108.40.206). First generation products are not suitable on Bake-hardening substrates because of higher curing temperatures. The suitability of the base steel for welding, brazing and mechanical joints has to be investigated according to 220.127.116.11, 18.104.22.168 and 22.214.171.124.