Black Coating for Steel
Do you have any suggestions on what solutions we might explore for black coating steel?
Q. I am the marketing manager for a metal fabricator and have a question on a black coating for steel. The items to be coated are wire hooks for hangers. Volume is roughly 100,000 lbs of steel per year. Previously, we coated the hooks using a blackened zinc chromate, but environmental regulations put in place last year have made this approach cost-prohibitive. The only affordable solution we’ve had access to since then is using a phosphate coated in oil, but the phosphate quality is low (brown discoloration) and the oily surface is not acceptable in the long-term to our client. For the time being, our client is sourcing from China, where zinc chromate is still cheap. The client would like to order from us again if we can find a solution as cost-effective as phosphate and oil, but with quality similar to the blackened zinc chromate.
The solution needs to be dry—no oil. Corrosion resistance is important, but less important than finish quality and low price. Do you have any suggestions on what solutions we might explore? B.A.
A. Both the phosphate and oil process and the blackened zinc chromate process are relatively inexpensive compared with any painting process. If corrosion resistance becomes a concern, you may still have to phosphatize the hooks prior to painting them. The dip-painting method is the simplest. Another option is the dip-spin process. If you use a baking enamel, you also will need an oven, which will add to finishing costs. Contact the paint suppliers listed at pfonline.com for their material recommendations.
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