The Cost of Electrocoating

Question:

Why is electrocoating equipment so expensive? Are there options that can reduce the cost, or how do I justify the expenditure? R.R.

Answer:

Electrocoating has always been labeled "capital intensive" in comparison to liquid or powder coating. While this is somewhat correct, but for a true comparison, the whole process must be evaluated.

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Any finishing system consists of the following four basic elements:

1. Material handling (some type of conveyor system);
2. Pretreatment (usually spray or immersion cleaning and phosphating);
3. Coating application (immersion for electrocoat and usually spray for liquid or powder); and
4. Curing (usually direct gas-fired oven with the correct time and metal temperature maintained). Each area will be addressed separately.

Because of the coating process, electrocoat will produce a higher part density (pieces per foot of conveyor) and, therefore, will require less conveyor to produce the same number of parts per hour. A decision between square transfer and linear conveyor will need to be made. If a linear conveyor is chosen, a decision between power-and-free or continuous movement is the next decision. Power-and-free and square transfer are the most expensive options, but provide the greatest flexibility.

Pretreatment will vary from a minimal 2-3 stage system up to 12+ stages, depending on the required quality performance and amount of waste treatment required. The pretreatment system is usually the most expensive component of the finishing system and the most critical for quality. It is also the biggest energy user (especially if spray) of the entire system. While most electrocoats provide superior corrosion resistance to the substrate, a lesser pretreatment system could be used compared to powder or liquid for the same corrosion properties.

The coating application equipment for electrocoat is very expensive due to the process and pH of the cathodic coating. However, the 100% coverage of the part (excluding air pockets) with a uniform, controlled dry film thickness, at 95+% transfer efficiency is a significant offset to the overall coating cost. If the older anodic coating technology is adequate for the product, the equipment cost can be reduced by using fewer stainless steel components and no anolyte control system.

The cost of curing equipment is dependent on the time and metal temperature required to cure the coating. Electrocoat will be comparable to powder and probably greater than liquid on similar parts. Some electrocoats are being developed to cure at lower temperatures. Low-cure powders are also being developed, but usually result in lower performance properties, like the low-cure electrocoats. Another energy factor to consider in comparison to liquid is the heat required for air make-up units to provide the air exhausted from the spray booths.

Before assuming electrocoat is too expensive, consider all of the factors and look at the true total cost per sq ft. The payback of electrocoat by controlling film thickness and first-pass transfer efficiency also needs to be considered over the long term.