Exhibit 31.2

CERTIFICATION

I, Thomas B. Testa, certify
that:

|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|-- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
|1. | I have reviewed this
  annual report on Form 10-K of GenTek Inc.;                                                                                                                                                                                                                                                                              
|   |                                                                                                                                                                                                                                                                                                                                                
|2. | Based on my knowledge,
  this report does not contain any untrue statement of a material fact or omit
  to state a material fact necessary to make the statements made, in light of
  the circumstances under which such statements were made, not misleading with
  respect to the period covered by this report;                             
|   |                                                                                                                                                                                                                                                                                                                                                
|3. | Based on my knowledge, the
  financial statements, and other financial information included in this
  report, fairly present in all material respects the financial condition,
  results of operations and cash flows of the registrant as of, and for, the
  periods presented in this report;                                                
|   |                                                                                                                                                                                                                                                                                                                                                
|4. | The registrants other
  certifying officers and I are responsible for establishing and maintaining
  disclosure controls and procedures (as defined in Exchange Act Rules
  13a-15(e) and 15d-15(e)) and internal control over financial reporting (as
  defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and
  have:
|   |                                                                                                                                                                                                                                                                                                                                                
|   | a)                                                                                                                                                                                                                                                                                                                                              | Designed such disclosure
  controls and procedures, or caused such disclosure controls and procedures to
  be designed under our supervision, to ensure that material information
  relating to the registrant, including its consolidated subsidiaries, is made
  known to us by others within those entities, particularly during the period
  in which this report is being prepared;         
|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|   | b)                                                                                                                                                                                                                                                                                                                                              | Designed such internal
  control over financial reporting, or caused such internal control over
  financial reporting to be designed under our supervision, to provide
  reasonable assurance regarding the reliability of financial reporting and the
  preparation of financial statements for external purposes in accordance with
  generally accepted accounting principles;                
|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|   | c)                                                                                                                                                                                                                                                                                                                                              | Evaluated the
  effectiveness of the registrants disclosure controls and procedures and
  presented in this report our conclusions about the effectiveness of the
  disclosure controls and procedures, as of the end of the period covered by
  this report based on such evaluation; and                                                                                                      
|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|   | d)                                                                                                                                                                                                                                                                                                                                              | Disclosed in this report
  any change in the registrants internal control over financial reporting that
  occurred during the registrants most recent fiscal quarter (the registrants
  fourth fiscal quarter in the case of an annual report) that has materially
  affected, or is reasonably likely to materially affect, the registrants
  internal control over financial reporting; and
|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|5. | The registrants other
  certifying officers and I have disclosed, based on our most recent evaluation
  of internal control over financial reporting, to the registrants auditors
  and the audit committee of the registrants board of directors (or persons
  performing the equivalent functions):                                       
|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|   | a)                                                                                                                                                                                                                                                                                                                                              | All significant
  deficiencies and material weaknesses in the design or operation of internal
  control over financial reporting which are reasonably likely to adversely
  affect the registrants ability to record, process, summarize and report
  financial information; and                                                                                                                
|   |                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                  
|   | b)                                                                                                                                                                                                                                                                                                                                              | Any fraud, whether or not
  material, that involves management or other employees who have a significant
  role in the registrants internal control over financial reporting.                                                                                                                                                                                                                   

|                     |  |  |  |                                             
|-------------------- |  |  |  | --------------------------------------------
|Date  March 17, 2008 |  | 
|                     |  |  |  | /s/
    Thomas B. Testa                     
|                     |  |  |  | Thomas B.
  Testa                           
|                     |  |  |  | Vice President and Chief
  Financial Officer

---