Surface Treatment Options for Die Cast Parts
Each treatment solves a different problem
Our process provides anodising, powder coating, plating and chromate conversion. Start from what has to be achieved: corrosion resistance in service, wear resistance on a sliding or threaded feature, appearance on a visible surface, or an electrical property at a contact or ground path. Anodising builds a hard oxide layer integral with the aluminium; powder coating adds a polymer film; plating deposits metal; chromate conversion supplies a thin chemical layer used alone for mild protection or as a pre-treatment beneath paint. The cost of each differs far less than the cost of choosing the wrong one and discovering it at assembly.
Difficulties start when a finish is specified for appearance while the real requirement is functional. A decorative powder coat over a mating face changes the fit and can insulate a ground path that was assumed to be continuous. A plating specification on a part that also holds tight tolerances means coating thickness must be allowed for in machining, not discovered later. Naming what each surface has to do, rather than merely naming a finish, gives us something we can actually engineer against.
The alloy sets what is achievable
Our standard alloys are ADC10 and ADC12 aluminium, AZ91D magnesium and Zamak zinc alloys, with custom alloys available per specification. Aluminium accepts anodising well, which is why our heat sink castings are normally supplied anodised - and because that finish also changes surface emissivity, it should be selected together with any thermal role rather than decided afterwards. Zinc alloys suit small high-precision components where a bright metallic appearance and good plating response are both wanted on the finished part. Tell us early which alloy is fixed and which is still open, because the available finishing routes sometimes narrow once one of them has already been chosen.
Magnesium deserves separate attention in design. It is more anodic than most metals it will meet, so contact with steel, copper or aluminium fasteners in a damp environment sets up galvanic corrosion unless it is designed out through isolation, coating or managed drainage. Those measures belong on the drawing rather than in the finishing instruction, because once the part is assembled nobody can insert insulation afterwards. Where such contact exists, raise it during DFM and we will propose a compatible protection route for the specific assembly.
Keeping finishing inside the process chain
Die casting, CNC machining, surface treatment and QC run under one roof in our 22,000 square metre facility, which removes the transport delays and duplicate inspection that appear whenever finishing is subcontracted elsewhere. Automated finishing supports consistency at volume. Practically it means the datum used at the casting stage and the figures in the final inspection report describe the same part, and a tolerance issue discovered after coating can be traced back through its batch instead of being argued about across two suppliers.
Quality documentation covers ISO 9001 and IATF 16949 with RoHS and REACH, and our QC laboratory provides salt-spray testing, CMM inspection and full batch reports to support qualification. The useful request is simple: state the finish, the surfaces it applies to, and any surfaces that must stay uncoated - particularly threads, contact faces and sealing areas. A drawing that excludes those specific surfaces costs nothing to produce and prevents a coating dispute later. DFM review is free, and we reply within 24 hours.
FAQ
Which surface treatments do you provide?
Anodising, powder coating, plating and chromate conversion are all available in-house. Selection depends on the alloy, whether the part carries heat or electrical contact, and the operating environment; we review that during free DFM analysis and return a quotation within 24 hours.
How is corrosion resistance verified?
Salt-spray testing is carried out in our QC lab alongside CMM inspection, and full batch reports are available. Tell us the required test duration and standard at enquiry stage so verification is included in the quotation rather than added after production has started.
Should the finish be decided before machining tolerances?
Yes. Coating thickness affects fit, threads and any surface used for sealing or electrical contact. Specify which areas are to be coated and which must remain bare on the drawing, so machining allowances can be set correctly before the first part is cut.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.