Legal Question in Business Law in California

Did ownership ever pass to the customer? If not, you probably can. We would need more details for a fuller answer.

I don't agree with the previous answer, but have a problem giving you a fuller and more nearly correct answer because your question leaves so many facts to guesswork.

First, what is your role here? Are you (1) selling steel and also painting the sold steel for an additional charge? or (2) is the customer bringing steel that it owns to you for painting services? or (3) something else?

In either situation (1) or (2), it is somewhere between "possible" and "likely" that you have a special lien on the steel until the invoices for painting that particular steel are paid. See Civil Code, section 3051. However, you would have greater difficulty asserting a lien against steel sold to or delivered for painting by the customer in January for payment of invoices for services performed with respect to painting invoices dated, say, October 2012.

A lawyer would perhaps also need to look at the terms of sale to see if there are provisions as to when and where title passes in order to determine your right to withhold delivery under the Commercial Code.