MacDermid Enthone Masco 400 DM Removes Zinc Phosphate Layers

Heavy duty, low-foaming liquid alkaline cleaner also works on oils, grease, soaps and solid lubricants.

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A de-phosphating tank line with dip spin centrifuge at WMV, which designs and builds automated and manual machines that treat mass produced bulk parts.


MacDermid Enthone Industrial Solutions has developed Masco 400 DM, a heavy-duty, low-foaming liquid alkaline cleaner designed to remove zinc phosphate layers as well as oils, grease, soaps and solid lubricants.

Ron Cucuro, the North America hard chrome and surface finishing product manager for MacDermid Enthone, says Masco 400 DM is usable in dip spin, rack and barrel processes.

“It is specially formulated to minimize the shortcomings of conventional alkaline formula approaches,” Cucuro says. “In addition, Masco 400 DM copes exceptionally well with the build-up of forming lubricants in the bath without creating excessive foam and can clean and de-phosphate components in the same step.”

Zinc phosphates are commonly used in the cold-forming of fasteners, wire and tube drawing, and pipes, with the phosphate layer functioning as a lubricant carrier and barrier between the work piece and tool. Cucuro says that after cold-forming the components will have a phosphate pressing pattern on their surface that consists of zinc or zinc-calcium phosphate and lubricants.

When fasteners are heat treated after cold-forming, Cucuro says the process can be negatively affected by the phosphate pressing pattern, resulting in an increased sensitivity to cracking and inter-granular corrosion.

“Any phosphate residue present on the surface during the non-oxidizing annealing treatment also leads to a diffusion of phosphorus into the marginal zone,” he says. “This contributes to sensitivity of the components to stress corrosion cracking and increases the probability of failure especially for high tensile fasteners.”

To avoid these problems, Cucuro says the residual phosphate and lubricant layer must be removed prior to heat treatment, and that’s what Masco 400 DM is designed to do.

“Simple alkaline de-phosphating systems quickly lose effectiveness due to contamination,” he says. “This results in having to increase application time and bath concentration to achieve consistently good results. These simple systems tend to produce foam which tends to solidify and is then dragged through the entire system.”

He says that conventional alkaline cleaners also fall short since substantial amounts of lubricant build up in the bath and tend to solidify or gel when cooled below 149°F.

The process steps for Masco 400 DM de-phosphating are: cleaning at >49°F for 4 minutes; de-phosphating at >49°F for 4 minutes; rinse at 149°F for 2 minutes; rinse at 149°F for 2 minutes; rinse at 149°F for 2 minutes; dry at 230°F for 2 minutes.

Product quality control is achieved through the use of a colorimetric test called the “blue test”. A surface of the component is immersed in a chemical solution which reacts with any residual phosphate present to form a blue color. The intensity of the color is proportional to the amount of phosphate present.

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