Tag Archive for: Conversion Coating

AD Chemicals has more than 40 years of experience in developing, manufacturing and worldwide supply of a wide range of metal surface pre-treatment chemicals. Pre-treatment is an essential process on metal products that are coated to provide a durable and attractive finish. AD Chemicals draws knowledge and expertise from across the range of AD International chemical disciplines to provide customers with the best possible advice from a leader in its field. This results in robust and reliable processes that are efficient and cost effective.

AD is known in the market for its innovative and market exceeding chromium(VI)-free conversion coatings that meet or outperform hexavalent based treatments. Products are marketed under the “PreCoat” brandname. Many surface treatment operations desire certification by industry organizations, especially when applied to new and technically driven products. Customers have come to rely on AD Chemicals to assist in or lead the certification process. All products meet or exceed current market standards such as GSB, Qualicoat, Qualisteelcoat and MIL.

Latest innovations:

PreCoat Z31: Cromium(VI)-free multi-metal conversion coating, tailored to the high demands for duplex coating applicators (powder coating over hot-dip galvanized steel). Only European alternative that performs equal to chromium(VI). Meets the Qualisteelcoat and GSB standard. Winner of 2016 Dutch Innovation Award for surface treatments. Also Qualicoat(A-119) approved for aluminium.

PreCoat TVL: Multi-metal (iron, steel, galvanized) passivation to upgrade the iron phosphating process, enables corrosion protection over 1000 hours NSS. Exceeds Qualisteelcoat standard and has a Qualicoat (A-095) approval for aluminum.

PreCoat A34: Based on a high-tech aerospace technology. Chromium(III) based conversion coating that enables bare metal corrosion protection in combination with excellent paint adhesion and corrosion resistance, Qualicoat (A-126) approved.

PreCoat CF: Complete chromium-free conversion coating for aluminium. GSB and Qualicoat (A-021) approved. No rinse system.coversion coating PreCoat chromium-6 free

Aluminium alloys are extensively used in space programs for both structural and non-structural applications. As well known, the corrosion resistance of these alloys is quite limited and anticorrosion treatment is needed.

The most used treatment currently used for improving the corrosion resistance of aluminium alloys are usually chromate (CrVI-based) conversion coatings (CCC). Due to the high environmental impact of these compounds, the REACH Regulation of the European Union decided to limit/restrict the use of hexavalent chromium. A sunset date of mid-2017 has been already set.

For the time being many chromate-free alternative products are available but they have found to be significantly inferior in terms of corrosion protection performances with respect to the chromate options. In this regard there is a great need to develop high performance hexavalent chromium-free anti-corrosion coatings with low environmental impact and conformity with the EU regulations.

The European Space Agency (ESA) is currently involved in a TRP contract with Instituto de Soldadura e Qualidade (ISQ) that is currently on-going. The objective of this study is to evaluate the anticorrosion behaviour of the different alternative pre-treatments applied to the most used aluminium. The outcome of this activity will be the identification and the optimization of the most promising anticorrosion pre-treatment.

Several commercial Cr(VI) free processes were applied onto aluminium alloys (2024-T3 and 2024-T81) used in the construction of ESA spacecraft, in order to investigate their anticorrosive properties compared with Alodine 1200, a widely used conventional CCC. One of these commercial processes (PreCoat A32) presented good anticorrosion performance, even better than Alodine 1200 and these results are presented in this paper.

Salt spray resistance is included in the testing program as well as metallurgical coating evaluation that include microscopy (SEM) observations before and after testing and electrochemical impedance spectroscopy (EIS), in order to evaluate surface and microstructural modifications due to degradation mechanisms. Further studies must be performed with the this promising alternative, modifying application parameters, in order to achieve improved corrosion protection efficiency.

Key Words: Aluminium alloy, Conversion coating, Anti-corrosion coatings, SEM, EIS

Source: Whitepaper Springer.com,Journal of Coatings Technology and Research, pp 1–14, Alternative corrosion protection pretreatments for aluminum alloys

Interested in PreCoat A32 passivation or the full whitepaper? Contact chemicals@adinternationalbv.com