The use of stainless steel honeycombs in catalytic converters is on the rise in Germany and could impact the world market, according to a recent survey performed by Eldib Engineering & Research, Inc., a firm in Berkeley Heights, NJ. Eldib found that although stainless steel itself is slightly more expensive than ceramic, the overall metallic system is smaller than the ceramic structure. Therefore it requires a smaller amount of expensive precious metals (platinum, rhodium and palladium), which are applied to both stainless steel and ceramic substrates in a thin layer and act as the catalyst that purifies gas before it escapes the tailpipe. In addition to being cost effective overall, stainless steel honeycomb catalytic converters are more efficient, decreasing environmental hazards because the level of pollution is reduced, as stainless steel is more durable and efficient for converting noxious gases into safe ones. In fact, metal foils, the material used to make the metallic structure, improve conversion by 15%. Considering that since the

Eldib conducted a series of interviews through which it surveyed the use of metallic versus ceramic honeycomb structures in 2000 models by various car manufacturers in Germany and France. German manufacturers using stainless steel in some models include Volkswagen, Audi, BMW and Daimler-Chrysler (Mercedes Benz). Porsche uses stainless steel in its two models. French carmakers use stainless steel on a much more limited basis. The conclusions drawn by Eldib could have major implications for the world market. 

Eldib maintains that the 2000 numbers on the two types of honeycombs reveal an increased use in metallic honeycombs in Germany, with limited use in France. The estimated total number of automobile catalytic converters used in Germany was 6.77 million units, 1.66 million of which contained metallic honeycombs and 5.11 million contained ceramic honeycombs. In France, during the same year, the number of catalytic converters totaled 2.8 million units, 191 thousand of which contained metallic structures and 2.6 million contained ceramic. German-based BMW, however, provides a salient example of the projected changes in the market. In 2000, the total number of converters used by BMW was 1,523,239, with 1,008,393 units containing stainless steel and 514,393 containing ceramic honeycombs, depending on the model. Overall, Eldib projects that by 2004 the market will see a 15-20% growth in the use of metallic honeycombs in both Germany and France. Use of ceramic honeycombs in both countries is expected to increase only 3% by the same year.

A huge market already exists for stainless steel foils, particularly in Japan. Specifically, confidence in the growth of stainless steel honeycombs is reflected by the recently announced plant by Kawasaki Steel Corp. to raise its output of stainless steel foil used in automobile catalytic converter honeycombs to 500 tons per month by the year 2003. The foils will be used for honeycombs put in converters in Japanese cars sold domestically and exported worldwide.

Eldib’s survey concludes that future trends in the European catalytic converter market suggest an increased demand for metallic honeycombs, the foils of which are as thin as cigarette paper. Because more than 75% of emissions are produced in the initial 90-120 seconds after starting an engine, German and French carmakers are considering a small pre-catalytic converter close to the engine. The pre-catalyst would be followed with a main underfloor catalytic converter that would be moved from the underfloor to a position closer to the engine. Heat losses would need to be reduced from the exhaust system. An electrically heated pre-catalyst would bring the main catalyst to the full operating temperature in seconds. A converter close to the engine would demand sufficiently high heat durability, as temperatures reach 1050 degrees Celsius. Thinner walls in the honeycombs create a more fragile structure plus increased vibration when placed closer to the engine. Not only will the current market for converters containing metallic honeycombs increase, but the future market will also see an increased demand, given that stainless steel honeycomb structures contain the thin, yet durable walls appropriate for a monolith support system.