This Small Business Innovation Research (SBIR) Phase I project aims to develop a pre-paint treatment product without using chromates and phosphates for applications in metal-finishing industries. Chromates and phosphates are still widely used in pre-paint treatments, but are environmentally undesirable. Replacements have been proposed and implemented, e.g., in the coil coating industry, but such systems are less robust and require tighter control of processing conditions. Other systems, such as silanes, need to dry and cure prior to painting. Such treatments cannot be used under a cathodic electrocoated paint. In this project, a product that can be electrocoated within 2 minutes after the pretreatment will be developed. The performance is expected to be as well as chromates or phosphates on a range of different metals. The interactions between silanes and the additions, as well as the structure and properties of the films will be studied. The anticipated results will be a number of environmentally-compliant metal pretreatments that can be electrocoated.
The broader/commercial impact of this project will be the potential to eliminate chromates and phosphates in pre-paint treatments without the loss of performance. The potential applications will be in automotive manufacturing, aerospace, steel industry (coil coatings), consumer electronics, appliance industry and many other industries where electrocoating is used for painting. An important societal impact will be the better protection to workers in plants, as this process is not toxic and will not require elaborate waste disposal procedures. This project will also enhance the scientific understanding of the mechanisms by which pretreatments contribute to the protection of metals.
This Small Business Innovation Research (SBIR) Phase II project aims to increase the utilization of metal surface treatment chemical products that provide significant environmental and health benefits, demonstrate improved adhesion and corrosion resistance over currently available chromate- and phosphate-free products, and reduce the total cost of manufacturing. This project will also extend the base of knowledge on this advanced pretreatment and will thereby leverage into an even wider impact over time as other companies strive to match this product’s performance. The market activity will in turn increase the acceptance and penetration for green high performance pretreatment products even further. The primary environmental benefit of this product (SILSBOND) over currently used phosphate pretreatment is the reduction of iron, zinc, and phosphate chemicals. The use of iron and zinc phosphate produces large amounts of high metal and phosphate containing sludge. This waste must be treated thus adding cost and risk to the manufacturing process. After treatment, residual metals still remain which require disposal. There are also harmful discharges of phosphate to the environment. Additionally, the product that ECOSIL has developed can be used as a sealer for other treatments or as aluminum pretreatment. Both of these applications will decrease the use of carcinogenic chromate-based products. Alternate products have been introduced to the industrial markets that provide similar environmental benefits to those of SILSBOND, but they have not penetrated the broader surface treatment market due to their lacking the robustness comparable to the phosphate processes. SILSBOND has been shown to produce improved anti-corrosive performance and robustness over similar products, and will therefore increase market penetration of this environmentally friendly product. Figure 1 and Table 1 illustrate the characterizations and tests used to understand the mechanisms that resulted in this improved performance. One of a number of reasons why coating adhesion is better with SILSBOND is the contour of the film. Although the film formed by SILSBOND is very thin, it creates a large surface area that promotes coating adhesion. In this study, the film surface area was characterized using Atomic Force Microscopy (AFM). Figure 1 shows the AFM images of a finely-polished CRS substrate before and after SILSBOND deposition. It can be clearly seen that the SILSBOND film exhibits a profile that dramatically increases surface area. Table 1. Comparative corrosion resistance of powder paint coated steel panels after 500 hrs. of salt spray test (ASTM B117) using SILSBOND versus phosphate pretreatment Pretreatment Ranking* SILSBOND (Cr-free, phosphate-free) 10 Iron phosphated (commercial product) 5 Zinc phosphated (commercial product) 5 Zinc phosphated, sealed with hexavalent chromium sealer 10 * Ranking from the best to the worst: 10 to 0 (in accordance with ASTM D 1654) The broader commercial impacts of this project will be to dramatically reduce the cost and complexity of metal surface pretreatment and sealing employed in manufacturing processes. The benefits of this product are based on reducing the number of steps required as compared to using currently available phosphate based products. The majority of products in use today require a) application of heat to the treatment baths up to 60 degrees C, b) require from 7 to 10 process steps, c) produce a large quantity of waste requiring disposal and d) are a magnitude thicker than the SILSBOND coating requireing higher chemical use. SILSBOND can be used at ambient temperatures, reduces the number of process steps to 3 to 5, produces 90% less waste, and is easier to control in the process. Phosphate free products being used commercially today have demonstrated process savings from these factors on the order of 30% of the total costs of pretreatment and sealing. SILSBOND will provide comparable levels of savings while providing improved performance over these products. Because of the increased penetration projected for SILSBOND, the total industry savings represents a large reduction in manufacturing costs, and will help to make US manufacturing more cost competitive with other countries.
