The Basics of Phosphate Conversion Coatings

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...]

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...]

Routine Maintenance in the Finishing Shop

Years ago on there was a television ad for a car repair shop that encouraged people to change their oil and brakes as well as maintain their fluids in the car. The tagline was simple: “Pay me now or pay me later.” Unfortunately in a metal finishing shop the same statement is true. Equipment maintenance in a metal finishing shop is often considered nothing more than an inconvenient hassle at the bottom of every plant manager’s "To-Do" list. However, with a little bit of proper care and some attention to planning, equipment can operate for longer periods of time without failure and dreaded … [Read more...]

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...]

Innovative Technology: TECHNICOAT 360 Ultra

TECHNICOAT 360 Ultra is Asterion’s latest development in high corrosion zinc passivation technology meeting RoHS requirements. TECHNICOAT ZNBL 360 ULTRA is a unique economical to use, all trivalent , high corrosion, thin film passivate for electrogalvanized zinc.  When properly applied to electroplated zinc it will produce a consistently blue bright finish that can meet 192 hours of neutral salt spray to white corrosion products without a top coat or seal. (ASTM 117B).  TECHNICOAT ZNBL 360 ULTRA can be used as a trivalent yellow when used with TECHNICOAT ZNBL 360 ULTRA YD. When added to … [Read more...]

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...]

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...]

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...]

Phosphating at Low Temperatures for Ferrous Metals

Phosphating at ambient temperature and at high temperature both have weaknesses.  Room temperature phosphating produces large amounts of sediment and slime, shows poor wear and corrosion resistance, and can produce fungus.  Phosphating at high temperatures (145-160 degrees F) will result in high energy consumption, as well as greater chemical consumption. Phosphating processes at lower temperatures (110-120 degrees F) has shown the strengths in producing a fast coating forming rate, low energy consumption, manageable sludge beds, and good corrosion resistance. Iron phosphate conversion … [Read more...]