Does the sale of a tax-delinquent property at a tax sale constitute a contract between the purchaser and the state?

Because the sale of tax-delinquent property to a private purchaser at a tax sale constitutes a contract between the purchaser and the state (see Anglo Cal. Nat. Bank v. Leland, supra, 9 Cal.2d at p. 352, 70 P.2d 937), plaintiff contends defendants are bound to disclose known, hidden defects just like any other private sellers of land. Plaintiff cites Civil Code section 1635, which states: "All contracts, whether public or private, are to be interpreted by the same rules, except as otherwise provided by this Code."