Thin Organic Precoatings
|Publication Date:||1 September 2019|
Note: Not recommended for spot welded or projection (fastener) welded applications without GM Manufacturing Approval.
Thin organic precoatings are applied on zinc-plated coil material by no-rinse technique. To realize good adhesion, chromium-free adhesion promoters are used. For improved adhesion and creep back resistance, a passivation can be applied before the application of the adhesion promoter itself. The thin organic precoating can be based on different polymer systems like epoxy, polyurethane, polyacryl, or polyester. GM Global Manufacturing Engineering Body-in-White Execution Center approval required for all welded applications prior to release.
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.
This standard covers the requirements for thin organic precoatings applied to a hot dip coated or electro-galvanized sheet steel substrate. One-sided thin organic precoating are not recommended due to error proofing and supply complexity. The substrate may be cold rolled (CR) or hot rolled (HR) sheet steel. First generation products are not suitable on Bake-Hardening (BH) substrates because of higher curing temperatures.