Skip to content

Cleaning & Conversion Coatings (Phosphating)

  • Cleaning and pretreatment are critical steps that ensure adhesion and corrosion resistance for any subsequent coating.
  • Diverse equipment enables Giering Metal Finishing to clean & pretreat one to millions of parts per order.
  • Inline washers are integrated into all of our automated finishing systems
  • Our immersion lines offer chemical cleaning, pretreatment and oxidation/rust removal using acid pickle if media blasting is not an option for your application.
  • Our media blasting service provides a means for a clean, pure metal surface to apply our finishes. We use aluminum oxide, glass bead, plastic bead, baking soda, walnut shell and other available media.
  • We have a variety of pretreatment processes which enable us to offer:
    • Zinc Phosphate
    • Iron Phosphate
    • Aluminum Conversion Coating
    • Wash Primer
    • Zirconium
  • Our pretreatment processes meet the following military specifications:
    • TT-C-490 type I Light, Paint-Grade Zinc Phosphate (TACOM/US Army Tank certified)
    • TT-C-490 type II Iron Phosphate
    • TT-C-490 type III acid wash pretreatment primer
    • TT-C-490 type V heavy-grade zinc phosphate…subsequent oil application option available
    • MIL-C-5541 / MIL-DTL-5541 Non-chromate Aluminum Conversion coating that is ROHS compliant

Part cleaning is only the first important step to proper finishing technique; pretreatment is the critical step for paint adhesion & corrosion resistance. The cleaning process removes oils, soils & other contaminants from the surface, providing a fresh substrate to deposit a pretreatment foundation for paint to adhere to. Below are the various types of pretreatments that we offer:

Zinc phosphate

Zinc phosphates provide maximum corrosion protection and extended service life to steel substrates. Zinc phosphate (Zn3(PO4)2) is an inorganic chemical compound used as a corrosion resistant coating on steel surfaces either as part of a subsequent organic finishing operation like wet paint, powder coating or electrocoating. Zinc phosphates have become the preferred pre-paint treatment in the products finishing industry and are pretty much standard in automotive & military industries. Zinc phosphate provides better corrosion resistance and paint adhesion than iron phosphate, especially under more demanding conditions.

TT-C-490, the federal specification for paint-based phosphate coatings, covers type I, light paint grade zinc phosphate (150 mg/ft2 min – 500 mg/ft2 max) and a type V, heavy grade zinc phosphate (500 mg/ft2 min – 1100 mg/ft2 max) which is normally followed by a subsequent oil application to preserve.

Paint-based zinc phosphate formulations can be applied to substrates other than zinc-plated and steel parts like galvanized steel, cadmium plating and aluminum. Phosphate solutions include nitrate, chlorate and iron accelerated types, nickel- fluorides, calcium-modified, and manganese-modified (tri-metal or polycrystalline) formulations applied by spray or immersion processes. We prefer immersion processes for a more uniform, total surface application where as spray can be limited to line of sight.

Iron phosphate

Iron phosphates produce an amorphous coating on steel, galvanized and aluminum surfaces. Iron phosphates act to enhance the adhesion of paint and powder coat on multi-metal parts after cleaning. Iron phosphating has been the process of choice for applications where overall cost considerations override all maximum performance needs. Since iron phosphates are thinner coatings than zinc phosphates and only contain the metal ion of the substrate being processed, they provide reduced corrosion resistance compared with a zinc phosphate. However, with environmental restrictions becoming increasingly tight with respect to heavy metals, an iron phosphate coating coupled with thorough post treatment may offer a viable alternative while still meeting required corrosion-resistance specifications. Our iron phosphate pretreatment systems meet the requirements of TT-C-490 type II.

Wash Primer Pretreatment

Wash Primer pretreatment is a wet spray pretreatment type. It is a 2 component acid catalyzed vinyl wash coat paint system. Wash primer promotes excellent adhesion, is compatible with a wide range of topcoats & is extremely fast dry for re-coat. Wash primer pretreatment serves to enhance adhesion of the coating system on nonferrous metals, ferrous metals, and plated surfaces. Paint system conforms to Military Specification DOD-P-15328D, TT-C-490 type III & Navy Formula 117.

Aluminum Conversion Coatings/Chromate/Chem Film

SafeGard CC-3400 is a conversion coating that is extremely effective on aluminum, magnesium and zinc. On Aluminum you can get both the clear and gold color from the same tank. On aluminum, Safegard CC-3400 provides excellent unpainted corrosion resistance and creates excellent base for paints and powder coatings WITHOUT the environmental burden of chromates.

SafeGard CC-3400 provides best overall adhesion and corrosion resistance combination. In extensive testing performed at the Naval Air Development Center, SafeGard CC met the requirements for paint adhesion and even outperformed its “chromate” counterparts. It has also been used as a replacement for light anodizing. A major European telecommunications company is now using SafeGard CC on to meet Europes ROHS Directive for the elimination of hexavalent chromium in Electrical and Electronic Equipment effective July 2006. California has already passed legislation to fall approximately in line with the EU timescales. They are using SafeGard CC-3400 with SafeGard CC-3400seal#2 for their corrosion and electrical conductivity on their aluminum parts. SafeGard CC has been tested by Boeing in St Louis. MO. They also agree that it passes both the corrosion and electrical conductivity requirements for MIL-DTL-5541 (formerly MIL-C-5541).

Phosphating processes can be separated into two types: iron phosphate and zinc phosphate.