FAQ

The product name is “CHEMEON TCP-HF” and a single component product HF simply stands for “Hex Free”.

The trivalent chromium coating layer does not have any entrapped water, but the main reason why it is not self-healing is because of the valences. Hex chromate can be reduced to Cr3+ (hydroxide and oxide) on the bare substrate, but trivalent chromium coating is not capable of being reduced. Also, hex chromium is mobile in an aqueous environment. On the other hand, trivalent chromium is in the form of precipitate and immobile. That means it cannot diffuse to the scratched area to heal the defect. Finally, the hexavalent coating loses it’s self healing properties and forms micro fissures which promote corrosion when heated over about 140º F. The trivalent does not.

CHEMEON TCP-HF is a liquid and is sold in 5/gal pails, 55/gal drums, 330/gal totes as well as 1.5oz touch-up pens and 16oz spray bottles.

Cured CHEMEON TCP-HF coating is ceramic in nature and does not have any entrapped water in the coating layer. This makes the coating harder than hex chromate coatings.

CHEMEON TCP-HF provides adhesive bonding layer on the metal surface at least as good as hexavalent chromate does. Dry tape, wet tape, and filiform corrosion (scribed and top-coated CHEMEON TCP-HF panels) under neutral salt spray were mainly tested for the adhesion properties.

No, in fact CHEMEON TCP-HF requires no agitation for the processing of the parts. You can agitate to mix the solution prior to processing however.

Regular alkaline cleaner can be used to clean the tank. Use scotch-brite to remove the hex chromate marks and residues on the tank walls and the tank bottom. Do a thorough DI or RO rinse before charging the bath with CHEMEON TCP-HF.

CHEMEON TCP-HF Touch-Up Pen can be used on parts that were previously processed with hexavalent chemistry. Of course, in order to ensure good performance, the area to be applied should be free of any oils and grease and totally clean.

The presence of trivalent chromium will not “reactivate” the surface or otherwise cause the hexavalent chromium to spread on the part or pen tip.

The chemical resistance of PVC is good enough to be a tank material for CHEMEON TCP-HF at temperatures less then 140º F. The only problem is that the PVC is not an environmentally green plastic; and therefore, not a recommended material by CHEMEON.

One of the reasons usually given for not recommending stainless steel for tank material is its susceptibility to chloride pitting. Excess chlorides over time may start a micro-pitting process and ultimately stress corrosion cracking. Chlorides are probably the single biggest enemy of stainless steel. Next to water, chloride is the most common chemical found in nature. In most environments, however, the PPM is so small the effects on stainless steel are relatively miniscule. In extreme environments, such as an indoor swimming pool, the effects over time can cause stress corrosion cracking. Gold and platinum in their natural state, are the only elements to be completely corrosion proof. But stainless steel has proven over time, in thousands of applications to be the best material to combat the elements that cause corrosion.

Other than the extreme exposure of chlorides, low acid levels with elevated temperatures, stainless steel such as 304 and 316 have been used for years in the metal finishing industry and are very good tank materials for CHEMEON TCP-HF; to a limited degree 317 & 347 SS materials have been used as well. SS is mostly resistant to chlorides, fluorides, oxidants and acids, extremes in these elements over time can cause problems. Mild steel on the other hand is not recommended as a tank material as it is a low carbon steel, is much softer, is malleable and ductile and bends fairly easily. Mild steel tanks can be lined, however, with polyvinyl chloride (PVC) or PVDC among others.

Note: Many CHEMEON TCP-HF customers have been using SS tanks for many years without incident.

CHEMEON TCP-HF is not an FDA approved product at this point. It is possible that CHEMEON TCP-HF coated surface can be safely in contact with neutral and non-corrosive food. If it is for coating the cans to store the pickled food (or canned food) it will require chromium free coatings with stain resistance.

CHEMEON TCP-HF EPA does not exhibit self healing characteristics.

Yes. CHEMEON TCP-HF EPA is QPL-81706B approved.

CHEMEON TCP-HF SP is QPL-81706B approved for spray only. It is currently under evaluation at NAVAIR for QPL approval for immersion.

The deoxidizing step is especially critical for parts with dirty oxide layers. A good surface activation step will allow better and homogeneous CHEMEON TCP-HF SP coating deposition on the metal surface. If the parts are newly machined and free of dirty oxides, then it is possible to skip the deoxidizing step before CHEMEON TCP-HF SP. Otherwise, it is always a good and recommended practice to activate the surface prior to the coating application to get repeatable performance results.

We do not recommend mixing the CHEMEON TCP-HF SP with any other product, including Alodine T5900. We do not know the long and short-term compatibility of Alodine chemical with CHEMEON TCP-HF SP. The other concern is the type of contaminants currently present in the Alodine T5900 bath. A newly charged CHEMEON TCP-HF SP bath would eliminate all these problems.

CHEMEON TCP-NP behaves like CHEMEON TCP-HF with black dyes, which is to say it doesn’t hold very well for dye applications; leaching is the typical result.

An alkaline cleaning stage is still needed when processing with CHEMEON TCP-NP, but no activation stage (deoxidizer, caustic etch). After the alkaline cleaning bath, rinse, then into the CHEMEON TCP-NP tank.

CHEMEON AA-200 Additive is comprised of several proprietary organic monomers. The Anodal EE liquid (Clariant) additive is organic acid based. It is not recommended to mix CHEMEON AA-200 with any competitor product.

CHEMEON AA-200 does not replace Teflon PTFE’s but does give a mild lubricious surface advantage and can be seen as complimentary to PTFE’s as CHEMEON AA-200 is interstitially bound throughout the oxide whereas PTFE is not. (See CHEMEON Continuing Education in Anodizing – Anodizing Reference Manual, pgs. 7 and 8, as evidenced by CHEMEON studies: Figure 2-Wear Resistance and Table 1-Wear Resistance).

Also, without going in depth on PTFE post hard anodizing application, I will submit this: PTFE is a topical application to enhance coefficient of friction but has an ephemeral life as it is worn off very shortly. CHEMEON AA-200 consisting of several organic monomers has the advantage of being integrated into the oxide columnar walls during the hard anodizing process. (Note: PTFE is only used for Type III hard anodic coatings as it is for wear surface activity.) Hence, CHEMEON AA-200 is an integral part of the total oxide and has virtual lifetime benefit as opposed to the fleeting life of topically applied PTFE.

CHEMEON AA-200 foaming is considered “normal” and not indicative of a larger problem. It is a result of the air agitation in the tank. Customer can use a defoamer or simply wipe away the foam.

Anodic thicknesses can range from .3 mils up to 1.5 mils depending on the quality of the castings and surface finish. Castings that are time-saved or mechanically surface finished afford the best opportunity for maximum oxide growth. However, caveat’s abound even with a good surface finish: silicon content; distribution and segregation of silicon; copper content (380 die-casts have a copper content of 3-4%; recall that 2024 alloys have a copper content of 3.8-4.9% and the difficulty in preventing burning); random Ra surface finish on different areas of the part, etc.In this situation the aluminum levels are borderline low: we recommend a range of 6-13 g/l. Aluminum levels below 4 g/l run the risk of burning especially during the ramp. Oftentimes 40-45º F will contribute to greater oxide growth using controlled current. Preparing the die-cast surface in the pre-cleaning stage with a nitric/HF (CHEMEON 3400-3600) will help immeasurably by removing silicon off the surface. (Silicon does not convert to an oxide as it dissolves throughout the oxide and is an impediment to a linear coating.)

Note: The reasons for burning are attempts to add oxide beyond the oxide thickness equilibrium and the high copper content and, as stated earlier, very low free aluminum bath levels. If this shop is running by amps and not getting the desired thickness it may be advantageous to back off the amps, limit the voltage and dwell the parts beyond the voltage set point. This will still not guarantee the desired thickness; but it may help. Again, die-castings traditionally are the most notorious alloys to achieve desired and constant oxide thicknesses.

In terms of the processes they are trialling with CHEMEON AA-200- in general,

– straight oxalic with CHEMEON AA-200: CHEMEON has no history using CHEMEON AA-200 with oxalic acid

– sulfuric with oxalic acid and CHEMEON AA-200: CHEMEON has no history using sulfuric acid, oxalic acid and CHEMEON AA-200

– straight sulfuric with CHEMEON AA-200: CHEMEON has a strong successful history processing wrought and die-cast aluminum alloys using CHEMEON AA-200 in concentrations of 6-8% for hard anodic coatings.