The phosphate process is the treatment of a metal surface that produces a reasonably hard, electrically non-conducting surface coating of insoluble phosphate that adheres to the underlying metal. It is used to enhance corrosion resistance, lubricity or as a foundation for subsequent coatings or paint. Zinc and manganese phosphates are also used to help break in parts subject to wear and to prevent galling. Zinc phosphate is often used with sodium stearate for lubrication in forging processes. It may be applied to a variety of substrates. Main Types of Phosphates The main types of phosphates … [Read more...]
March 5, 2015 By
Chromate Conversion Coatings
Zinc is typically used for the electrodeposited coating for iron and steel when prevention of atmospheric corrosion is the primary objective. However without a subsequent treatment, typically chromate, electrodeposited zinc becomes dull and grey and will quickly develop white corrosion products after exposure to air. Chromate conversion coatings impart both an aesthetically pleasing finish as well as varying degrees of corrosion protection. The use of Chrome VI in the conversion coatings as the passivation agent for zinc deposits are endowed with numerous advantages. These include: High … [Read more...]
September 12, 2014 By
Hexavalent to Trivalent (and Back Again)
As the demand for non-chromium protection of zinc and zinc alloy plating has increased, trivalent chromium passivation systems have appeared. Early on, an interesting phenomenon was observed: Hexavalent chrome was found on coatings that were not supposed to contain hexavalent chrome. It was thought that the processor must be cheating and using hexavalent chrome in the working solution in order to achieve increased corrosion resistance. While all of the questions have not been answered, there are some conclusions. Before explaining the various parts of this mystery, it's important to … [Read more...]
October 14, 2013 By
Watts Nickel Bath: Basis for Modern Nickel Plating
When looking at the chemistry of the Modern Nickel Plating solution, you have to go back to the early 1900’s; 1916, to be more precise. Watts began plating nickel with nickel sulfate, nickel chloride and boric acid. These components are the basis of all modern bright, semi-bright, microporous and high-sulfur formulations used today. While the combination is always the same, the amounts differ some by bath type and manufacture. To compare the original formulation to the bright nickel levels, here are the typical levels: 1916 2013 Range Nickel … [Read more...]
September 19, 2013 By
Functional Zinc Processes
Zinc is one of the most widely used functional sacrificial coatings to inhibit corrosion of ferrous metals. Over the years a variety of Zinc plating and post treatment chemistries (chromates –hexavalent and trivalent-- and seals) have been developed to improve the aesthetics and functionality of zinc coatings. Over the years there have been three types of zinc processes: Cyanide based chemistry – seldom used today because of safety issues, waste treatment and disposal cost—but still it is needed in some applications. These processes were very forgiving and easy to control. Environmental … [Read more...]
September 10, 2013 By
Trivalent Chromates 101
To coat metal parts, chromates are used to enhance the life of the part. Typically, chromates are used on zinc plated parts whether it be alkaline non-cyanide or chloride applications. These trivalent chromate conversion coatings offer prolonged corrosion protection to finished parts. In the past, hexavalent chromates were predominantly used throughout the metal finishing industry. Today, to meet RoHS compliances and environmental safety standards, the metal finishing industry has moved in the direction of trivalent chromates. Trivalent conversion coatings have shown to produce a scratch … [Read more...]