H&W Global Industries offers excellent zinc phosphate coatings, both fine-grain and heavy-grain. All of our coatings are continuous, uniform in texture, and evenly distributed. We conduct all tests as required in the specification, at our state-of-the-art facility.
Fine-grain is an excellent pretreatment for steel prior to painting. It offers moderate bare corrosion protection. This fine-grain conversion coating method is for the pretreatment of ferrous metals and zinc/zinc alloy coated metals before paint is applied, as per the requirements of Federal Specification TT-C-490 and Military Standard MIL-DTL-16232.
The bath concentration, temperature, and immersion time for parts assure that the phosphate coatings meet all the requirements of the specification. The equipment used for the fine-grain bath is constructed of materials resistant to the action of the phosphating solutions. Phosphatized parts are not allowed to dry between the phosphatizing solution treatment and the subsequent cold running water rinse. Fog sprayers or other means are used for prevention of drying until the final rinse.
Control of the chemical content of the phosphate coating solutions consists of free acid, total acid, and ferrous iron. Unless otherwise specified, the frequency of testing for free acid, total acid, and ferrous iron is made prior to starting production. High production rates may require more frequent analysis to assure process control within established limits.
Heavy-grain is a pretreatment for steel often required in military applications. In general, heavy-grain coating in this application is thicker and coarser. It places more sacrificial zinc on the surface, creating more corrosion resistance.
Prior to beginning the zinc phosphate coating process, the parts are thoroughly cleaned of oil, grease, wax, dirt, scale, and other foreign matter, and will not show visible signs of red corrosion products.
Adequate rinsing is performed following any chemical process to remove residual material. Special care is exercised in rinsing complex shapes to prevent contamination of any subsequent process. Care is also exercised to ensure complete drying in crevices, seams, or other difficult-to-dry places prior to painting.