Surface coatings can cost an awful lot of money, but the quotes given are often based on secret formulas, and it is astonishing just how some items can cost so much more than others.
Part Size and Batch Volume
Larger articles need more chemistry for coating, occupy more space on tanks or in spray booths and generally require longer processing times. While the cost per article can decrease with large articles by processing them in batches, the cost per article will increase for single large articles as setup time and consumables are spread over fewer articles.
Base Material and Preparation Needed
The substrate is key and affects the surface treatment costs. Surface treatment processes for aluminium, steel and stainless steel differ significantly in terms of the pre-treatment required prior to application of the surface coating. Some substrates even require more aggressive surface cleaning and local etching prior to coating.
Coating Type and Process Complexity
Many surface treatment processes are applied at room temperature using straightforward chemistry. Some processes however are operated at high temperature in a number of stages or at very precisely controlled current density. These processes are often applied using specialised plants which are controlled in very strict environmental conditions. Examples of such processes are described in surface treatment of metals: process guidance note 4/01. See also Surface Treatments.
Masking and Tolerance Requirements
If certain features of your component are to remain uncoated then this will significantly increase the cost of the component. Additionally if there are very tight finished dimensions then these components may require grinding or lapping after plating to obtain the required dimensions.
Quality Documentation and Certification
Additional costs also arise as a result of the administration necessary to complete a job, such as issuing a full process certificate, provision of test coupon results, or production traceability. Administration time can often cost as much as a simple preparation activity and for Aerospace/Defence work in particular, there can be considerable additional costs involved in meeting the necessary documentation requirements.
Knowing about these factors will help you to ensure that parts are specified in the best way to get a cost-effective surface treatment without compromising on quality.
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